#precalculus

1 messages · Page 31 of 1

willow bear
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loosely, linear algebra is the study of vector spaces and linear transformations between them

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if you ask me to elaborate i will tell you to study it 🗿

compact spade
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this doesn't intuitively seem possible

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is it

river drift
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what is the size of each matrix? What has to match for the two matrices to be multiplied?

compact spade
winter comet
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um

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actually

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i mean its not possible

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but its not because the sizes aren't exactly the same

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uhh

compact spade
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what

winter comet
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basically you gotta make sure the number of columns in the first matrix has the same number of rows in the second matrix i think

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idk how to explain

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wait i swapped them lol

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💀

river drift
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you had it right the first time...

winter comet
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did I

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bro im confusing myslef

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💀

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what am i doin 😔

river drift
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you can think of the entry in the i'th row and j'th column of the product matrix as the dot product of the i'th row vector of the first matrix, and the j'th column vector of the second matrix

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for such a product to be defined, such vectors must be the same length

burnt wolf
winter comet
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but you can't multiply them, right?

winter comet
burnt wolf
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You can multiply them!

winter comet
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if you're adding or subtracting they have to have the exact same dimensions...

burnt wolf
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Yeah

winter comet
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right

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ok

river drift
burnt wolf
kind schooner
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AB is 3x2 * 3x3, BA is 2x3 * 3x3

compact spade
winter comet
compact spade
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no

winter comet
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hmm

compact spade
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if i did i wouldn't be here

winter comet
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true

compact spade
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:(

river drift
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let's put it this way: A is 3x2, B is 3x3. you need the "inside dimensions" of AB: 3x2 3x3 to match

kind schooner
compact spade
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idk man

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the bad one

burnt wolf
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Ohhh, the last thing I’ve learned was composing matrices 💀

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I have no room to speak here

kind schooner
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it looks like precalc w/limits by ron larson

winter comet
compact spade
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sounds like it

river drift
burnt wolf
winter comet
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i haven't actually done matrices in a while

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so i keep tripping up and being unsure 💀

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i need to review them lol

surreal crescent
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Just hear me out:

1/3=0.333…
3(1/3)=1
3(0.333…)=0.999…
0.999…=1

kind schooner
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thas crazy

winter comet
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technically...

surreal crescent
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And that’s calc boys and girls

winter comet
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literally lol

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like with respect to limits, yes that does check out

river drift
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the calculus involved is making the number "0.333..." have any particular meaning in the first place

surreal crescent
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Is limits that fancy f

winter comet
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you're probably thinking of integrals

surreal crescent
winter comet
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limits

river drift
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if you mean $\int$ that's an "s" (an old fashioned variant called the "long s")

obsidian monolithBOT
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pnoןɔ

winter comet
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integrals

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yea

surreal crescent
burnt wolf
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I’ve gotten through everything up to limits without finishing Algebra II or Pre-calculus 💀

winter comet
burnt wolf
surreal crescent
burnt wolf
winter comet
river drift
surreal crescent
river drift
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everything in calculus is really a limit in disguise

burnt wolf
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Indeed-y

winter comet
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so like

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f(x) = x

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from -2 to 2

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the shaded region is the integral

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except the negative area cancels out with the positive area

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so i don't know why i used a confusing example

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💀

surreal crescent
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So it’s

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$S(-2,2)$

obsidian monolithBOT
surreal crescent
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Why did I think that would work

winter comet
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lol

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i think its like

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backslash int_lowerbound^higherbound

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or something

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not sure

river drift
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the integral $\int_a^b f(x) \odif{x}$ is the (signed) area between the function $f(x)$ and the $x$-axis between the points $x=a$ and $x=b$. because of the fundamental theorem of calculus'', it turns out that the integral is an operation related to the anti-derivative'', so we use $\int f(x) \odif{x}$ to mean the ``anti-derivative'' of $f(x)$, i.e., the function whose derivative is $f(x)$

obsidian monolithBOT
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pnoןɔ

winter comet
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we're making this look way more complicated than it is

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just take a funciton. its a line right? take the area between that line and the x axis, and thats the integral

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lol

surreal crescent
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$int_-2^2$

obsidian monolithBOT
winter comet
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hmm

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didnt work 💀

obsidian monolithBOT
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Root
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

winter comet
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oh lets go kinda worked not really

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😭

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maybe its .

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not _

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i'm not sure

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don't take my word for it i'm really not sure

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lol

river drift
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the _ worked as intended, but it only includes one character by default

surreal crescent
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$\int_-2^2f(x)$

river drift
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to include more characters, enclose it in braces: _{-2}

winter comet
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oh

surreal crescent
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$\int_{-2}^2f(x) $

winter comet
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well that kind of worked........?

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good enough i guess 💀

surreal crescent
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It’s like learning to code exept it’s only /print

burnt wolf
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For real 😭…

winter comet
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💀

river drift
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you can click the reaction to get the error message

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the problem is that you backslashed the dollar sign

winter comet
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i thought you sighed lol

surreal crescent
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$\int_{-2}^2f(x) \ $

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Well now that just didn’t work

river drift
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no spaces before the ending $

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delete the backslash at the end

surreal crescent
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$\int_{-2}^2f(x)$

obsidian monolithBOT
surreal crescent
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Yay

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wtf does the / do

river drift
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\ is a prefix for latex commands

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for example, \$ is a command that prints a dollar sign (the dollar sign otherwise is a signal to start/end math mode), \int prints an integral sign, \frac prints a fraction, etc

surreal crescent
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Huh, anyways ima go to bed, I don’t think math is a good eneugh exuse to get 5 hours of sleep

compact spade
river drift
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do you know how a system of linear equations corresponds to a matrix equation?

river drift
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so then you are trying to find if, in part 49a, [ \begin{bmatrix} x \ y \end{bmatrix} = \begin{bmatrix} 2 \ 1 \end{bmatrix} ] is a solution to the system of linear equations

obsidian monolithBOT
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pnoןɔ

agile sparrow
compact spade
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i dont feel like you need matrix multiplication for that...

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hmm

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thank you though

agile sparrow
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Sorry not a for 50

river drift
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matrix multiplication comes out to the same operation as any other method, just in a different format

agile sparrow
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Oh yeah a for 50

compact spade
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you are a liar how dare you

agile sparrow
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Oh yeah it's B mb

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My mind calculation is fucked

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And I doubted the wrong one

compact spade
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This is word salad

river drift
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ok let's break it into steps

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first, write it as a matrix equation

compact spade
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how would i go about doing that

river drift
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ok so for example
[ \begin{cases} 3x_1 + 6x_2 = 7 \ 2x_1 + 3x_2 = 9 \end{cases} ] then by the way we define matrix multiplication, that's equivalent to: [ \begin{bmatrix} 3 & 6 \ 2 & 3 \end{bmatrix} \begin{bmatrix} x_1 \ x_2 \end{bmatrix} = \begin{bmatrix} 7 \ 9 \end{bmatrix} ]

obsidian monolithBOT
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pnoןɔ

river drift
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(you can multiply out the left side to see how that's true)

compact spade
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ok makes sense for now

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next thing?

river drift
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the next thing is to construct an augmented matrix

river drift
# obsidian monolith **pnoןɔ**

if we call the matrix equation in this example [ AX = B ] then we have: [A = \begin{bmatrix} 3 & 6 \ 2 & 3 \end{bmatrix}, \quad X = \begin{bmatrix} x_1 \ x_2 \end{bmatrix}, \quad B = \begin{bmatrix} 7 \ 9 \end{bmatrix} ]

obsidian monolithBOT
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pnoןɔ

river drift
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an augmented matrix is just a matrix where we've combined the entries of two different matrices into one for calculation purposes

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so in this example we have: [ \begin{amatrix}{1} A & B \end{amatrix} = \begin{amatrix}{2} 3 & 6 & 7 \ 2 & 3 & 9 \end{amatrix} ]

obsidian monolithBOT
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pnoןɔ

agile sparrow
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You're done

river drift
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the instructions say to use gauss-jordan elimination

compact spade
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yes and also i gotta understand the damn thing not just solve it

agile sparrow
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adj would be
3 -6
-2 3

river drift
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so in linear algebra, we have 3 basic row operations

agile sparrow
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And determinatant -3

compact spade
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please do not mention linear algebra those words scare me 💀

agile sparrow
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There u go

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Linear algebra

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Linear algebra

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Or maybe

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Higher algebra

compact spade
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ahhh terrified ahhh

agile sparrow
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Coordinate geometry

compact spade
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ok sorry cloud you can continue

agile sparrow
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Who's cloud

compact spade
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the helpful one

river drift
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the idea is that performing such operations does not change the set of solutions to our equation

agile sparrow
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So I am not helpful

compact spade
river drift
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the aim is to make a matrix equation with the same solutions, but which is easier to read. we call this "reduced row echelon form"

compact spade
proven geyser
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is it possible to skip pre calc over the summer

proven geyser
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without getting a B or below in ap calc

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ok

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is it like light light or light

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cause i lowkey already know half the shit they have on khan academy

compact spade
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possible? sure. feasible? idk, idk you or your cirriculum

proven geyser
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besides matrices and the advanced trig

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i am relativley good at math

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curriculum follows calc ab

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doesnt matter for pre calc cause its not in school

compact spade
proven geyser
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also

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when we use the word "mod" in pre calc is it reffering to abs value or actual remainder from division

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cause i was reading this master math trigonometry book and the topic was polar equations

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and it said mod was abs value

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but mod in cs and combinatorics means remainderf rom div

river drift
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most preferably, we would prefer our system of equations to look like:
[ \begin{cases} 1x_1 + 0x_2 = a \ 0x_1 + 1x_2 = b \end{cases} ] which in the augmented matrix format looks like: [ \begin{amatrix}{2} 1 & 0 & a \ 0 & 1 & b \end{amatrix} ]

obsidian monolithBOT
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pnoןɔ

compact spade
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so rref?

river drift
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yes

compact spade
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ok

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but how do we get from our current thing to that

river drift
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Gauss-jordan elimination is a procedure to apply row operations to make our matrix into reduced row echelon form (rref)

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our 3 row operations are:

  1. multiply a row by a scalar
  2. swap two rows
  3. add a multiple of a row to another row
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in principle there are many different sequences of row operations that can get you to RREF, but gauss-jordan elimination gives you a consistent procedure

compact spade
river drift
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unfortunately the amatrix environment is custom

compact spade
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how get from that to

compact spade
river drift
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I in my infinite wisdom picked an equation with no solutions. So choosing a different augmented matrix (we will follow the same procedure): [ \begin{amatrix}{2} 1 & 3 & 5 \ 2 & 7 & 14 \end{amatrix} ]

obsidian monolithBOT
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pnoןɔ

river drift
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The first step in Gauss-jordan elimination is to find the first pivot: this is the top left-most number

strong epoch
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Could someone help me with a at least probability question?

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I hated matrices bro

river drift
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if the pivot is 1, we will leave it alone. If not, we will multiply the whole row by whatever we need to in order to make the pivot 1

strong epoch
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So much work lol

compact spade
compact spade
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So usually it will be a fraction?

strong epoch
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Could I get help with question 9?

river drift
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yes, usually it's multiplying by 1/(something)

compact spade
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And you multiply the row?

river drift
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yes, so for example if we started with: [ \begin{amatrix}{2} 3 & 9 & 15 \ 2 & 8 & 14 \end{amatrix} ] then we would multiply the first row by $\frac{1}{3}$ to make the pivot 1: [ \begin{amatrix}{2} 1 & 3 & 5 \ 2 & 8 & 14 \end{amatrix} \begin{array}{l} R_1 \to \frac{1}{3} R_1 \ \mbox{} \end{array} ]

obsidian monolithBOT
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pnoןɔ

river drift
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once we've done that, we "eliminate" every entry below the pivot by adding a multiple of the current row

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so in this example, we'll add (-2) * the first row to the second row

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in order to make the 2 below the pivot into a 0

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[ \begin{amatrix}{2} 1 & 3 & 5 \ 0 & 2 & 4 \end{amatrix} \begin{array}{l} \mbox{} \ R_2 \to R_2 - 2 R_1 \end{array} ]

obsidian monolithBOT
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pnoןɔ

river drift
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next, we take a new pivot down and to the right of our first pivot, in this case the 2

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we again multiply the row by whatever's necessary to make the pivot 1:

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[ \begin{amatrix}{2} 1 & 3 & 5 \ 0 & 1 & 2 \end{amatrix} \begin{array}{l} \mbox{} \ R_2 \to \frac{1}{2}R_2 \end{array} ]

obsidian monolithBOT
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pnoןɔ

river drift
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since we've hit the bottom row we'll now eliminate above the pivot, to make whatever's above the pivot a 0 by adding a multiple of the second row to the first row

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[ \begin{amatrix}{2} 1 & 0 & -1 \ 0 & 1 & 2 \end{amatrix} \begin{array}{l} R_1 \to R_1 - 3 R_2 \ \mbox{} \end{array} ]

obsidian monolithBOT
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pnoןɔ

river drift
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now that we've achieved rref, the solution is made obvious. this seems like a lot of steps, but once you know the pattern it's mostly just rote work

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if you search "gaussian elimination" or "gauss-jordan elimination" on youtube or google i'm sure there will be plenty of other explanations as well

compact spade
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ok, thank you so so much

strong epoch
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Do you know about combinations and stuff ?

compact spade
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Me?

strong epoch
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Anyone

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I’m so confused

compact spade
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Ah ok

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I don't, good luck :(

strong epoch
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Thanks

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If anyone knows how to do it reading this isn’t it 1 - (probability of it not happening )

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So isn’t it 83 choose 7

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1- that

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I got it let’s gooooo

strong epoch
arctic sundial
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Mock exam today

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Wish me luck

willow skiff
candid mortar
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having trouble with these sort of questions. But the sheet full of them that i have dont come with solutions. On this one i got
(25-a^2) / a(5+a)

surreal crescent
willow bear
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25-a^2 factorizes

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(also the goal is to simplify, right?)

candid mortar
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yea id gotten caught up in my frustration toward this complex fraction business and didnt realize until i wrote it down here

ripe siren
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hi can anyone help me with 3 precalc math problems?

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so for the 3rd pic its the same option choice for both of the last question

willow bear
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@ripe siren do you still need help with these?

willow bear
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ok, let's start with the first pic, which i'll repost standalone for my own convenience

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any progress on this one so far?

ripe siren
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so i got someone to help me and for a) i got 27017.7 b) idk yet

willow bear
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can you tell me how you got 27017.7?

ripe siren
willow bear
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aight cool

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ok

ripe siren
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ye then i simlified it

willow bear
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you put it in a calculator.

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i wouldn't call that simplification.

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you were asked to round to 2dp and you did.

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... might wanna go to a help channel or wait

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@ripe siren ok so now you want to find the linear speed of a point at the edge of your saw

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do you know in general the relationship between angular speed and linear speed for circular motion?

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yes/no

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(no numbers yet!)

ripe siren
willow bear
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that's too vague

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do you know how to calculate linear speed given angular speed and radius?

willow bear
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right ok in that case

ripe siren
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srry i dont kow much math

willow bear
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let's step back a bit

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since there's something we need to go over

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instead of speeds let's talk about lengths first

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so you know what a radian is, yes?

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(yes i'm going somewhere with this, i just want to explain things fully before we get back to your problem)

ripe siren
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sorry i cut u off like that

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:((

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i didnt mean to waste ur time

willow bear
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bruh

ripe siren
willow bear
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i mean

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ok??

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do you still need anything from me?

ripe siren
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genuinely

willow bear
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cause now you've shown me that you will throw away any attempts of mine at giving you a coherent explanation (and not just feeding you a formula you could plug&chug into)

ripe siren
harsh basalt
willow bear
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no guarantees

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but deezniks and i appear to be done, so you can post your problem (in full) now

harsh basalt
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i need to use the function in the rectangular coordinate system

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which is pretty easy to get the mins/maxes

harsh basalt
willow bear
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if you want to grab my attention, DON'T do it by reply-pinging on a message that's got nothing to do with your question.

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anyway, furthest point from the origin just means r is maximized. so you need to take the max point for that you found in part A, and your point will have polar coordinates (f(θ), θ) with that value of θ.

harsh basalt
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sorry for doing that

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so would the x value of the max from part A be theta?

willow bear
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that's what i said, yes

harsh basalt
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alright thank you so much i appreciate the help

naive dock
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Anyone here good with angle of rotation?

willow bear
tender questBOT
viscid thistle
naive dock
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Find the angle of rotation for 13x^2+6sqrt(3)xy+7y^2-32=0

viscid thistle
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Bro

naive dock
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I got cot(2theta) = 1/sqrt3

viscid thistle
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Is that even precalculus?

naive dock
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It is

viscid thistle
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Sqrt????

naive dock
naive dock
viscid thistle
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Ahh

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What grade are you in? Just checking to know what's coming soon.

naive dock
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Im in college

viscid thistle
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Thank God.

naive dock
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2nd year 1st sem

viscid thistle
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Alright so I am safe fore a few years

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Angle of rotation as in those idk transformations?

naive dock
#

Wdym

mental fable
naive dock
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You use it to remove xy term I think

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It has a formula of cot(2theta) = (A-C)/B

viscid thistle
mental fable
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how old are u

viscid thistle
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11

mental fable
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oh hell nah

viscid thistle
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Lol

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15

mental fable
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oh nice im 16

viscid thistle
#

Am in grade 9

viscid thistle
#

10?

mental fable
naive dock
viscid thistle
mental fable
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11

viscid thistle
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Nice

mental fable
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im not too sure about these grade things

viscid thistle
#

Ohh shit, imma be 16 when I finish 10

mental fable
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cus i learnt the stuff youre learning when i was 14

viscid thistle
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Lucky lol

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Well, smart actually

queen shoal
#

how do you find derivatives of functions

willow bear
#

@queen shoal here, you might wanna give these a watch to start with.

fiery creek
#

if so I can walk you through it

arctic sundial
# willow skiff Good luck!

I got a 5! 38/40 for mcq and idk about frq yet but I def got more than 4 points out of 24 to meet the minimum for a 5 bc we went over one FRQ in class today

quiet merlin
#

Does anyone know how to do these number 6,7,9,11,12

viscid thistle
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Wait what

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No

quiet merlin
viscid thistle
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Someone else???

crisp hinge
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I'm in algebra 1, i just am learning this stuff

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but what are integrals? and what are derivatives?

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and what are hyperbolic sine/cosine/tangent

summer ruin
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you shouldn't worry about this in algebra 1

crisp hinge
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no i should because half of my class is foreshadowing for this

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and its like

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what you're learning is baby math

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compared to

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[insert trig or other stuff like calculus]

river drift
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almost all math is baby math compared to something. but math builds on itself, so you have to have a solid foundation

crisp hinge
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true

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but I stil dont know what that stuff is

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can u explain?

summer ruin
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well the simple explanation isn't going to be useful and proper explanation isn't going to be short

crisp hinge
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i dont care

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im fine with the long explanation

summer ruin
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then you can just open a book/search the web/watch a lecture on it

crisp hinge
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i did

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but

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I need somebody to personify it

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because i dont understand what they say

summer ruin
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this is why you learn basic stuff first

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you're not going to find a lot of people that are willing to explain material for hours

crisp hinge
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true

summer ruin
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so it would be better if you have specific questions about stuff you don't understand

crisp hinge
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alright

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is altitude easier to explain?

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because i need to know all of this for math olympiad

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and im in 6th

summer ruin
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altitude?

crisp hinge
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so idk any of this

crisp hinge
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something about triangle

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s

summer ruin
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who knows

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you need to specify everything

crisp hinge
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i need to understand this

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could you draw an altitude from B?

summer ruin
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sure

crisp hinge
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so how would i do it?

summer ruin
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draw a straight line from vertex B to the side AC

crisp hinge
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does the angle have to be a right though?

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because then

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if it isn't it can be anything

summer ruin
crisp hinge
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if the point we are drawing from B to is named E

summer ruin
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the vertex can have any angle, the altitude always creates a right angle with the side it touches

crisp hinge
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then BEC

crisp hinge
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makes sense

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none of the resources i found said that

summer ruin
#

my first search result is wikipedia's page on altitude https://en.wikipedia.org/wiki/Altitude_(triangle)

In geometry, an altitude of a triangle is a line segment through a vertex and perpendicular to a line containing the side opposite the vertex. This line containing the opposite side is called the extended base of the altitude. The intersection of the extended base and the altitude is called the foot of the altitude. The length of the altitude, o...

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and it says it right there

crisp hinge
#

my browser is broken

compact spade
#

57 is impossible right

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plugged it into rref and it didn't work

river drift
#

,w rref {{5,-3,2,2},{2,2,-3,3},{-1,7,-8,4}}

obsidian monolithBOT
river drift
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it's not inconsistent, but it does have infinitely many solutions

compact spade
#

Oh shit

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Ok how do I prove that

river drift
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rewrite this back into a system of equations

compact spade
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i did

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x - 5z/16 = 13/16
y - 19z/16 = 11/16

river drift
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then you can solve for x and y

compact spade
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can i??

river drift
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just move the z term to the other side on each side

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then you have a formula for x and y in terms of z

compact spade
#

but thats in terms of z then

river drift
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yes, that's why there are infinitely many solutions

compact spade
#

so

river drift
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each value of z corresponds to a different solution

compact spade
#

ok got it

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ty

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:)

compact spade
#

not sure how to properly turn this into a system of equations

summer ruin
#

find the number of beef required to produce some amount of muffins, bones and cookies

compact spade
#

ohhh wow that's really really helpful thanks

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oh shit wait

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sorry

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i thought that was a sarcastic message until i reread it and you were unironically being helpful sorry 💀

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...i still do need a little more help though given that im stupid

summer ruin
#

since you want to find the number of muffins, bones and cookies it makes sense to give each quantity a variable to represent each number

compact spade
summer ruin
deft adder
#

The function f is given by f(x) = (sin(x) + cos(x)) (sin (x) - cos (x)).
A student is trying to solve f(x) = 1. Which of the following equations
could be used to find the values of x that solve the equation f(x) = 1?
A) cos(2x) = 1
B) sin(2x) = 1
C) cos(2x) =-1
D) sin(2x) =-1

How do i solve this? I feel like i get most of it but then I get stuck

chrome ether
#

what is “most of it”? show us what work you have

rugged harness
#

let's say i can calculate the volume of a rotating block by calculating the area of several smaller shapes that making up that block, can i calculate the area of that block by calculating the circumference of those shapes

#

well particularly the torus

queen shoal
viscid thistle
#

Though this is quite a difficult math

#

Is it related to functions?

river drift
#

it's introductory linear algebra

viscid thistle
river drift
#

linear algebra is usually taught at the college level, although some high schools teach a small amount as part of an algebra/precalculus curriculum

night elbow
willow bear
fiery creek
#

are you familiar with derivative rules @queen shoal

queen shoal
#

no

#

i dont know derivative

fiery creek
#

ok well that's a pretty tough derivative for someone who's never done derivatives before

queen shoal
#

i dont know chain rule either

fiery creek
#

i'd recommend learning the basics first

winter comet
winter comet
# queen shoal what are the basics

the derivative of ax^(n) = anx^(n-1), where a and n are constants

example:
lets say you want to find the derivative of 5x^2
here, a = 5 and n = 2.
thus, plug it into the "formula".
the derivative of 5x^2 = (5)*(2)x^(2-1) = 10x^1 = 10x

crisp timber
#

why is the derivative of x^n = x^(n-1)/n?
It is kind of noticeable that it is x^(n-1), but why is it divided by n?

summer ruin
#

why is the derivative of x^n = x^(n-1)/n?
it's not

#

,w d/dx x^n

obsidian monolithBOT
winter comet
#

make sure you aren't getting it confused with the antiderivative

crisp timber
#

True lol. But then, why is it multiplied by n?

winter comet
#

to prove the generalized chain rule you can always fall back on the definition of a derivative

#

i forgot exactly how they prove the chain rule

#

you can look it up if you want

#

but that's just what you do

#

you multiply it by n

limpid wasp
loud valve
#

does anyone know how to solve these

#

or these

barren gorge
#

hi

viscid thistle
#

Someone tagged me?

viscid thistle
willow skiff
#

The hint is very useful about negative numbers

#

Is your problem with how to get the domain or writing it in the given notation?

plush quail
#

Getting the domain

willow bear
#

do you know the domain of the raw square root function?

#

i.e. of just sqrt(x)

plush quail
#

I have to determine the domain

#

Thats all thats given

willow bear
#

you did not answer my question

#

if you don't know the domain of sqrt(x), then you should just say "no, i don't know the domain of sqrt(x)"

plush quail
#

No i dont

#

Idk the sqrt (x)

willow bear
plush quail
#

I think i did 5 right

#

More so need help with 6

#

Actually no if i did 5 i can do 6

#

Number 10 is what i truly dont understand

willow bear
#

ok...

#

do you know how to work with equations of straight lines in general?

plush quail
#

No

willow bear
#

do words like "slope-intercept form" ring any bells?

#

or stuff like y = mx + c?

plush quail
#

It sounds familiar, but i couldnt tell u what mx or c is from

willow bear
#

This Algebra video tutorial provides a basic introduction into linear equations. It discusses the three forms of a linear equation - the point slope form, the slope intercept form, and the standard form of the equation. This video explains how to calculate the slope of a line that passes through two points and how to graph a linear equation in...

▶ Play video

This algebra video tutorial provides a basic introduction into point-slope form. It explains how to write a linear equation given a point and the slope. It also explains how to write a linear equation given two points. Finally, it discusses how to graph a linear equation in point-slope form.

Algebra For Beginners: ...

▶ Play video
#

give these a watch, and perhaps also search youtube for "organic chemitry tutor straight line equations" and watch the other vids that show up.

#

and/or also do that but for khanacademy instead of ochem tutor.

lapis bramble
#

never trust cha.gpt 😅

#

it is not a good study tool

deft turret
#

I did it y’all

#

I got into ap precalc

#

The 2 weeks of staying up until midnight was worth it

winter comet
winter comet
#

unless it was talking about limits

#

then you ignore that kind of domain restriction

#

idk tho

lapis bramble
winter comet
#

oh

#

thats not even what i saw LOL

#

thats funny

lapis bramble
#

well cuz it canseled out x-64 and x-8 meaning their the same and also implying that -8=-64

winter comet
#

yeah

#

but they couldn't cancel it out anyway unless they noted that z != 8

#

thats what i saw originally

#

i didnt even notice the 64 💀

lapis bramble
#

lol

burnt wolf
#

I had no problem with it until I found out everything from Matrices and up aren’t on the exam, and they don’t cover any actual Calculus content. Like not even like an introduction to limits or anything. Half of the questions from practice tests I could answer just from my Algebra II knowledge!

winter comet
#

i realized i already knew everything they were gonna teach

#

so i just self studied the other stuff that they werent gonna teach

#

precalc is so undefined some of the classes are practically algebra 2 and some are actually purely stuff for calc

river drift
#

if a class taught calculus it would be called a calculus class...

burnt wolf
burnt wolf
winter comet
burnt wolf
river drift
#

the point of a precalculus course is to cover everything you need to know before a calculus course, not to teach the "first part" or "introduction"

burnt wolf
winter comet
#

i remember i looked at the syllabus for precalc and i was like "bruh i thought this was algebra"

burnt wolf
winter comet
#

i thought precalc was matrices, polar coordinates, conic sections mebbe, vectors, limits, probability? idk

river drift
#

what makes an ap course, an ap course, is that it offers college credit (in this case, for the type of precalculus course taught in college). nothing really more or less than that

burnt wolf
burnt wolf
#

AP classes are typically either the first semester, or the first-year of a college course

river drift
#

most colleges do offer a precalculus course for students who do not yet have the pre-requisite knowledge for a first-year calculus course

burnt wolf
river drift
#

for non-stem majors some colleges allow for their pre-calculus course to count for whatever math requirement they have. it's certainly not useful to every student, although that's also the case for any ap course

#

i think the broader issue is that the range of topics a "precalculus" course may cover is extremely wide, depending on the level of knowledge a calculus course expects you to know vs what they expect to teach you

burnt wolf
river drift
#

i don't know enough about the ap precalculus curriculum to know whether it is "college level" (which a precalculus course can be, as evidenced by the fact colleges offer them), but nothing about a course being "college level" implies it must teach calculus

burnt wolf
#

And those topics are not that difficult, at a Precalculus level, matrices are super easy to wrap your head around

sinful halo
#

@steep estuary

chrome ether
#

AP precalc is not college level.

#

that is the big thing that just makes me go "why are they even making this a thing" 😭

#

a lot of colleges will likely just not take it for credit, period

viscid thistle
chrome ether
#

ap PRECALC

#

not ap CALC

#

(which is also hardly """"college level"""")

viscid thistle
# chrome ether not ap CALC

Nah i know but like I was asking whether or not ap Calc Is college level. Follow up question, what can be considered college level then?

chrome ether
#

calculus is barely scratching the surface of actual undergraduate mathematics

winter comet
#

which would technically be 'college level'

viscid thistle
winter comet
chrome ether
#

the meatier parts of the undergrad curriculum begin when you start to move away from just endless computation and move towards proof-based stuff

viscid thistle
chrome ether
#

truth be told

#

the really substantial stuff is more at the graduate level

viscid thistle
#

I tried proof, understood some of it, but like it's quite conceptual I felt.

chrome ether
#

the most important undergrad courses are probably abstract algebra and analysis

chrome ether
viscid thistle
#

What's Complex anal?

#

Masters?

chrome ether
#

some undergrads take it

viscid thistle
#

Ahh I see

chrome ether
#

the point of undergrad is more to

#

develop the mathematical maturity you need for intensive graduate level research

willow skiff
viscid thistle
#

I probably won't even be picking maths in undergrad since I am going into bio but still it's quite interesting.

willow skiff
#

Cool

deft turret
#

At my school you have to be the top score’ers to get into ap calc

#

But that only applies to honors im2 I’m in regular im2

#

But there was space for ap pre calc so she gave it to me

#

But I do know that pre calc won’t be accredited as much as ap calc since college doesn’t teach or calc

#

Pre calc*

burnt wolf
viscid thistle
#

Hey guys

#

Need your help

#

I need to calculate the derivative of this function

#

I dont understand this moment

#

Why x^5 became x^2

river drift
#

they factored out an x

#

,, x^{5/3} = x^{3/3 + 2/3}

obsidian monolithBOT
#

pnoןɔ

viscid thistle
#

I still dont understand it

river drift
#

,tex \exprules

obsidian monolithBOT
#

pnoןɔ

viscid thistle
#

I understood it but another way

#

Anyways thanks

#

We can also figure it out this way: cube_root(x^5) = cube_root(x^3x^2). And then we basically get x^3 out of the root. xcube_root(x^2)

viscid thistle
clear scarab
#

,tex \integrationrules

#

,tex \intrules

#

,tex \help

warped cipher
willow summit
#

any one help me i have high school additional math exam in this year

willow bear
viscid thistle
#

Guys

#

Why (a^x)' = ln a * a^x

#

Can it be proved?

#

Or i should just remember it

#

Generally, i dont understand what a natural logarithm has to do with it

willow skiff
obsidian monolithBOT
willow skiff
viscid thistle
#

What is precalculus then?

#

What do you discuss here

willow skiff
#

Like logs, exponential functions, rational functions, sin, cos, tan etc

viscid thistle
#

Usually if i have smth regarding to trig, i go to trigonometry channel

agile sparrow
#

Let f : (0,1)   be the function defined as f ( ) x n  if 1 1,
1
x
n n
 
     
where n   . Let
g : (0,1)   be a function such that 2
1 () 2
x
x
t
dt g x x
t
    for all x(0,1). Then
0
lim ( ) ( )
x
f xgx 
(A) does NOT exist
(B) is equal to 1
(C) is equal to 2
(D) is equal to 3

modest bay
#

😧😧😧😧

agile sparrow
#

sorry

#

im so sorry

agile sparrow
#

shit

#

not this

viscid thistle
agile sparrow
viscid thistle
agile sparrow
proven void
#

,, \text{Find } a \text{ and } b > 0 \text{ such that the } \lim_{x \to \infty} \left( \frac{\sqrt{ax^4 + bx^3}}{x} - x \right) = 4.

obsidian monolithBOT
#

milanesa de pollo

willow bear
#

you don't have to do a million \text{} btw

#

you could have typed the same thing like this:

#

Find $a, b > 0$ such that $\lim_{x \to +\infty} \left( \frac{\sqrt{ax^4 + bx^3}}{x} - x \right) = 4$.

obsidian monolithBOT
#

|Ann⟩

willow bear
#

also show all your progress thus far.

proven void
#

is it bad to say status = 1

#

!status

tender questBOT
#
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
willow bear
#

for step 1 i suggest rewriting this thing as a single fraction

#

then you can do some bullshit with conjugates.

proven void
#

what now?

#

the conjugate of the numerator ?

agile sparrow
#

From root

#

That would give x^2

#

Take both x^2 common

#

And cut one x

willow bear
# proven void

recommend against manipulating the limit and dragging it all along with you

#

just work algebraically with the function inside of it

#

as mentioned earlier, do some conjugate bullshit

#

namely multiply top and bottom by sqrt(ax^4+bx^3) + x^2

agile sparrow
#

the limit is tending to inf

#

That would make it messier

willow bear
#

not any more so than any other limit with roots like this.

agile sparrow
#

It's useful when tending towards 0

proven void
#

I dont get it

willow bear
#

trust me it is still helpful here

willow bear
#

and so high is doing it in a somewhat hard to read way

proven void
willow bear
#

i have to go sleep tho so maybe it will have to be the blind leading the blind

agile sparrow
proven void
agile sparrow
#

a has to be 1

proven void
#

why?

agile sparrow
#

i solved it ]

#

in my mind

#

it could be not right

#

but it should be

#

my mind calc sucks

#

after u take x^2 common

#

u'd be left

#

ith]

#

x(underroot[a+b/x]-1)

#

underroot a+b/x-1 has to be 0

#

to create inderminant form

#

put the limit x = inf

#

b dissapears

#

and a=1

#

and b is 8

tender mist
river drift
proven void
#

I dont get it dammit

north anchor
#

what’s the formula for an alternating series like this? i cannot remember lol

river drift
#

alternating geometric series don't have a separate formula from other types of geometric series

agile sparrow
agile sparrow
#

1/5

#

1/26 is tat the ans

north anchor
agile sparrow
#

oh my fucking gad

river drift
tender questBOT
# agile sparrow 1/26 is tat the ans

As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.

willow bear
#

$\frac{(-1)^n}{s^{2n+2}} = \frac{1}{s^2} \cdot \paren{-\frac{1}{s^2}}^n$

obsidian monolithBOT
#

|Ann⟩

proven void
#

Represent the following sets on the line. Write them as intervals or as a union of intervals
${ x \in \mathbb{R} \mid |x| > 3 }$

obsidian monolithBOT
#

milanesa de pollo

proven void
#

sorry if its badly translated wtf should I do here?

#

in general if |x| < 3 that means
-3 < x < 3

#

but how is it for |x| > 3 tho

willow bear
#

well

#

|x| is the distance from x to 0 on the number line, yes?

proven void
#

yeah

willow bear
#

well

#

|x| > 3 means x is further than 3 units from 0

#

this should enable you to draw it on the number line

proven void
#

-3 > x > 3 maybe?

#

so strange smh

#

but I only know because if |x| < 3 then -3 < x < 3

willow bear
proven void
#

then prolly |x|>3 means -3 > x > 3

willow bear
#

i said draw on the number line

willow bear
#

do as i say

#

dont play 5D chess with my instructions

#

again

#

draw a number line

#

mark the points 3 and -3 on it

#

then color all of the points which are further than 3 units away from 0

proven void
#

I dont get it

#

What about it

willow bear
#

erase the gd -3 > x > 3

#

but yes the diagram is correct

#

thats what you were supposed to do

#

thats what i asked you to do

#

by the way -3 > x > 3 would translate to (-3 > x) AND (x > 3), but there's no point which satisfies both inequalities at once -- you cannot be under -3 while also being above 3.

proven void
#

That was the lesson learnt that the two side inequality is wrong

#

How to write that as union of intervals?

willow bear
#

well

#

how many intervals do you see marked on your diagram?

proven void
#

not sure

willow bear
#

look at it.

#

ok let me reproduce yours in somewhat better visual quality.

#

how many intervals are colored?

#

don't overthink this, i know for a fact that you're able to answer this.

#

im not asking you to do the whole thing at once. just do what i say.

#

do what i say nothing more. nothing more. dont do more than i ask for.

proven void
#

two

willow bear
#

right.

#

let's look at the first interval, on the left.

#

how do you write this in interval notation?

proven void
#

not sure if the ifinity is inclusive but
(-infty , -3) would be my guess, since you cannot include infinity

willow bear
#

you never include infinities.

#

but yes, (-∞, -3) is correct.

#

now look at the second interval, on the right.

#

what's that in interval notation?

proven void
#

(3, +infty)

willow bear
#

right.

proven void
#

I think I understood, tysm

viscid thistle
#

,tex \exprules

viscid thistle
river drift
#

read the pins in #latex-help for a more general introduction to latex

proven void
#

how can I graph $f(x) = cos(2x + \pi)$ just from knowing how to graph $g(x) = sin(x)$ and $h(x) = cos(x)$

#

?

agile sparrow
#

@proven void

proven void
#

wassup

agile sparrow
#

What's senx

obsidian monolithBOT
#

milanesa de pollo

proven void
#

typo, mybad

agile sparrow
#

Draw the graph of cos2x

#

and flip it upside down

proven void
#

,w plot cos(2x)

proven void
#

how do I flip it

agile sparrow
#

nah

#

I thought u meant on paper

#

Like for general understanding

#

Do u know how to plot cos2x=

proven void
#

no

agile sparrow
#

Draw cosx and shifts the point by half

#

Life π/2 becomes π/4 due to the 2x

#

And vice verse

#

cos(2x+π) the pie makes it shifts to the 3rd quadrant

#

thats why it flips

proven void
#

how do I

agile sparrow
#

anyway

proven void
#

graph

#

that

agile sparrow
#

cos2(x+π/2)

proven void
#

?

agile sparrow
#

2cos^2(x+π/2)-1

agile sparrow
#

I don't see the use of sinx graph in this

#

Also

#

meh

proven void
#

you dont need to use sin

#

its only if needed

#

I dont get it tho

agile sparrow
#

Well I hope u understand the graph

proven void
#

how to I sketch cos(x) ?

agile sparrow
#

Shift sinx

#

Graph

#

Making it start from 1

#

as cos 0 = 1

#

where 0s the x and 1 is the y

#

And at π/2 it's zero

#

Use desmos for reference

near sentinel
#

how do i do this

#

1/512 is the answer

#

its not in the Q

willow bear
#

$\lim_{x \to 0} \frac{(16+x)^{1/4} - \frac{1}{32}x - 2}{x^2}$

obsidian monolithBOT
#

|Ann⟩

willow bear
#

did i read the problem correctly?

#

@near sentinel

proven void
#

how to do this?

#

we got to clear the x^2 from the denominator no?

#

how to doe

willow bear
#

i think i'd rather wait for OP to give confirmation that i have the problem written correctly

proven void
#

@near sentinel

willow bear
#

assuming that it \textit{is}, i would rewrite $(16+x)^{1/4}$ as $2(1 + \tfrac{1}{16}x)^{1/4}$, and then expand that into its taylor series up to and including the $x^2$ term.

obsidian monolithBOT
#

|Ann⟩

willow bear
#

failing that (such as if op doesn't have access to taylor series), we could resort to l'hôpital's rule.

proven void
#

what are the conditions that need to be met so lhopitals is possible to be used?

proven void
#

taylor series?

willow bear
#

but the most important condition is that the limit is in either of the two forms 0/0 or ∞/∞.

#

here it is 0/0.

proven void
#

oh yeah its 0 numerator as well didnt noticed, again 2^4 = 16

willow bear
# proven void taylor series?

In mathematics, the Taylor series or Taylor expansion of a function is an infinite sum of terms that are expressed in terms of the function's derivatives at a single point. For most common functions, the function and the sum of its Taylor series are equal near this point. Taylor series are named after Brook Taylor, who introduced them in 1715. A...

#

(1+x)^p in particular has a known and simple(ish) taylor expansion.

proven void
#

? how so

willow bear
#

$(1+x)^p = 1 + px + \frac{p(p-1)}{2!} x^2 + \frac{p(p-1)(p-2)}{3!} x^3 + \dots$

obsidian monolithBOT
#

|Ann⟩

willow bear
#

this could also be obtained as a generalization of the binomial theorem (the generalization being that the exponent no longer has to be a natural number)

proven void
#

whats next?

near sentinel
willow bear
#

ok then i repeat my suggestion:

near sentinel
willow bear
#

expand (1 + x/16)^(1/4) into a power series up to and including the x^2 term

#

do some simplification

#

the answer will just pop out

#

if you don't have access to power series, then apply l'hôpital.

near sentinel
#

here's what I did, I rationalised the numerator and got until {16+x - (x/32 +2)^2]/32x^2

near sentinel
#

wait whats power series

willow bear
#

can you show your work for rationalization

near sentinel
#

i think ik it but with a dff name

near sentinel
willow bear
#

taylor? maclaurin?

#

does either of those names sound familiar?

near sentinel
#

yeah ik taylor

willow bear
#

then that is what i meant

near sentinel
#

my teacher did teach us aa method uding binomial expansion, but im not very good at it

willow bear
#

yeah binomial expansion is exactly what i am suggesting here.

#

$(1+x)^p = 1 + px + \frac{p(p-1)}{2!} x^2 + \dots$

obsidian monolithBOT
#

|Ann⟩

near sentinel
#

ohkk

#

If you dont mind can you please explain it to me

willow bear
#

explain what

near sentinel
#

the method; i tried it but i couldnt get rid of the x/32 and 2 term

#

ill send pic of my working

#

if i apply DS, im left with 1/x^2

willow bear
#

rewrite $(16+x)^{1/4}$ as $2(1 + \tfrac{1}{16}x)^{1/4}$ and then as $$2 \paren{1 + \frac{1}{4} \cdot \frac{x}{16} + \frac{\frac14 \cdot (-\frac34)}{2} \cdot \paren{\frac{x}{16}}^2}$$

near sentinel
obsidian monolithBOT
#

|Ann⟩

willow bear
#

you need the x^2 term from the expansion too

near sentinel
#

ohkk

#

ill try doing that

#

thank you!!

#

that way there will remain a term of x in the denominator

near sentinel
#

the x^2 term got cancelled

#

but the ans is wayyy off

#

ok not wayy off

#

close

#

but not accurate

#

where am i going wrong

#

hmm

#

i can try that

proven void
#

I got x^3 from the expansion and Is still not enough

#

did you managed to solve?

#

I still cannot

#

I dont think any other more terms will work because it cannot get cancelled with the denominators x^2

#

so will be zero, without providing any more preciseness, e.g. the third term of the expansion is x^3 something so it will result in something multiplied by x and since x is approaching zero . . .

#

if someone manages find out the answer ping me

proven void
# near sentinel

also I dont get it your prof is saying the answer is positive but when I try do it I also get the middle x^2 being negative

#

mm

#

whatever

near sentinel
near sentinel
proven void
#

💀

near sentinel
proven void
#

@willow bear , any idea?

near sentinel
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its actually a build up question

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ill send the prev q

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like its implied you have to solve it like the prev question

proven void
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did you rationalized for 3?

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or binomial expansion/ taylor series around x = 0

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?

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why is 4 repeated twice

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but with different functions

near sentinel
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thats a diff question, its like a hw assignment and our sir is too lazy to change index

near sentinel
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i got the answer for 3

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by rationalisation

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but im supposed to do it by binomial exp

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and the ans comes either way

willow bear
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,w lim[x -> 0] x^-2 * ( (16+x)^(1/4) - x/32 - 2)

obsidian monolithBOT
near sentinel
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💀

willow bear
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did your prof proclaim that the answer is positive?

near sentinel
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its a hw question; so i dont know until tomm

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ill ask

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and confirm

proven void
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I got the same number

near sentinel
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🫠

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i think i should ask my teacher

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cause smth is wrong

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with the question

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imo

proven void
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really nice question tho

near sentinel
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or the ans key

near sentinel
proven void
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whatever

hot kayak
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Help

hoary mountain
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What to do?

willow bear