#precalculus
1 messages · Page 31 of 1
what is the size of each matrix? What has to match for the two matrices to be multiplied?
sizes don't match, eg. impossible?
um
actually
i mean its not possible
but its not because the sizes aren't exactly the same
uhh
what
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
idk how to explain
wait i swapped them lol
💀
you had it right the first time...
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
for such a product to be defined, such vectors must be the same length
That’s only if you’re adding or subtracting
but you can't multiply them, right?
no its if your multiplying
You can multiply them!
if you're adding or subtracting they have to have the exact same dimensions...
Yeah
you can find BA but not AB
Why is that?
AB is 3x2 * 3x3, BA is 2x3 * 3x3
h
do you know how to multiply matrices?
no
hmm
if i did i wouldn't be here
true
:(
let's put it this way: A is 3x2, B is 3x3. you need the "inside dimensions" of AB: 3x2 3x3 to match
wait is this the same book im using what book is this
Ohhh, the last thing I’ve learned was composing matrices 💀
I have no room to speak here
it looks like precalc w/limits by ron larson
idk if you want to but this is gud video channel so its prob good video https://www.youtube.com/watch?app=desktop&v=2spTnAiQg4M&ab_channel=TheOrganicChemistryTutor
yeah probably
sounds like it
composing linear transformations represented by matrices is the same as multiplying matrices
Wait really? I’d no idea, better go practice now
i haven't actually done matrices in a while
so i keep tripping up and being unsure 💀
i need to review them lol
Just hear me out:
1/3=0.333…
3(1/3)=1
3(0.333…)=0.999…
0.999…=1
thas crazy
technically...
And that’s calc boys and girls
the calculus involved is making the number "0.333..." have any particular meaning in the first place
Is limits that fancy f
I just want to use the fancy f
limits
if you mean $\int$ that's an "s" (an old fashioned variant called the "long s")
pnoןɔ
It’s like if an asymtote was roided up
I’ve gotten through everything up to limits without finishing Algebra II or Pre-calculus 💀
limits are used for asymptotes... if thats wut ur saying
Now I’m drilling pre-calc so I can take it over summer with less difficulty
thats good
Yes but what does it mean
Yeah!
the integral means the area between the curve and the x axis
as the "s" suggests, it's a sort of sum (being calculus, it's really the limit of a sum we call a "riemann sum")
Of a particular point, or of like the point of derivative or smth
everything in calculus is really a limit in disguise
Indeed-y
i mean there are integrals with bounds
so like
f(x) = x
from -2 to 2
the shaded region is the integral
except the negative area cancels out with the positive area
so i don't know why i used a confusing example
💀
Root
Why did I think that would work
lol
i think its like
backslash int_lowerbound^higherbound
or something
not sure
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 $f(x)$
pnoןɔ
we're making this look way more complicated than it is
just take a funciton. its a line right? take the area between that line and the x axis, and thats the integral
lol
$int_-2^2$
Root
Root
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
oh lets go kinda worked not really
😭
maybe its .
not _
i'm not sure
don't take my word for it i'm really not sure
lol
the _ worked as intended, but it only includes one character by default
$\int_-2^2f(x)$
to include more characters, enclose it in braces: _{-2}
oh
$\int_{-2}^2f(x) $
It’s like learning to code exept it’s only /print
For real 😭…
💀
you can click the reaction to get the error message
the problem is that you backslashed the dollar sign
i thought you sighed lol
$\int_{-2}^2f(x)$
Root
\ is a prefix for latex commands
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
Huh, anyways ima go to bed, I don’t think math is a good eneugh exuse to get 5 hours of sleep
do you know how a system of linear equations corresponds to a matrix equation?
yes
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
pnoןɔ
a for 49 and 50
i dont feel like you need matrix multiplication for that...
hmm
thank you though
Sorry not a for 50
matrix multiplication comes out to the same operation as any other method, just in a different format
Oh yeah a for 50
how would i go about doing that
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} ]
pnoןɔ
(you can multiply out the left side to see how that's true)
the next thing is to construct an augmented matrix
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} ]
pnoןɔ
an augmented matrix is just a matrix where we've combined the entries of two different matrices into one for calculation purposes
so in this example we have: [ \begin{amatrix}{1} A & B \end{amatrix} = \begin{amatrix}{2} 3 & 6 & 7 \ 2 & 3 & 9 \end{amatrix} ]
pnoןɔ
the instructions say to use gauss-jordan elimination
yes and also i gotta understand the damn thing not just solve it
adj would be
3 -6
-2 3
so in linear algebra, we have 3 basic row operations
And determinatant -3
please do not mention linear algebra those words scare me 💀
ahhh terrified ahhh
Coordinate geometry
ok sorry cloud you can continue
Who's cloud
the helpful one
the idea is that performing such operations does not change the set of solutions to our equation
So I am not helpful
you're trying and that's helpful in terms of morale
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"
but im finding cloud's explanations more helpful personally rn
ok, makes sense
is it possible to skip pre calc over the summer
yes
without getting a B or below in ap calc
ok
is it like light light or light
cause i lowkey already know half the shit they have on khan academy
possible? sure. feasible? idk, idk you or your cirriculum
besides matrices and the advanced trig
i am relativley good at math
curriculum follows calc ab
doesnt matter for pre calc cause its not in school
sorry, the "makes sense" was an acknowledgement that i was getting it so far - i'm still not 100% of the way there
also
when we use the word "mod" in pre calc is it reffering to abs value or actual remainder from division
cause i was reading this master math trigonometry book and the topic was polar equations
and it said mod was abs value
but mod in cs and combinatorics means remainderf rom div
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} ]
pnoןɔ
so rref?
yes
Gauss-jordan elimination is a procedure to apply row operations to make our matrix into reduced row echelon form (rref)
our 3 row operations are:
- multiply a row by a scalar
- swap two rows
- add a multiple of a row to another row
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
still on this
unfortunately the amatrix environment is custom
how get from that to
that
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} ]
pnoןɔ
The first step in Gauss-jordan elimination is to find the first pivot: this is the top left-most number
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
So much work lol
I hate them too
Ok, makes sense
So usually it will be a fraction?
Could I get help with question 9?
yes, usually it's multiplying by 1/(something)
And you multiply the row?
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} ]
pnoןɔ
once we've done that, we "eliminate" every entry below the pivot by adding a multiple of the current row
so in this example, we'll add (-2) * the first row to the second row
in order to make the 2 below the pivot into a 0
[ \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} ]
pnoןɔ
next, we take a new pivot down and to the right of our first pivot, in this case the 2
we again multiply the row by whatever's necessary to make the pivot 1:
[ \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} ]
pnoןɔ
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
[ \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} ]
pnoןɔ
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
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
ok, thank you so so much
Do you know about combinations and stuff ?
Me?
Thanks
If anyone knows how to do it reading this isn’t it 1 - (probability of it not happening )
So isn’t it 83 choose 7
1- that
I got it let’s gooooo
1 - 83C7/108C7
Good luck!
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)
The best way I’ve found is the use and actual division symbol-➗ (in case you forgot, lord knows I have) between the fractions, then put any non fraction terms above 1 and flip and multiply it out
that's correct but you can simplify it further still
25-a^2 factorizes
(also the goal is to simplify, right?)
yea id gotten caught up in my frustration toward this complex fraction business and didnt realize until i wrote it down here
ill give this a go
hi can anyone help me with 3 precalc math problems?
so for the 3rd pic its the same option choice for both of the last question
@ripe siren do you still need help with these?
yes pls
ok, let's start with the first pic, which i'll repost standalone for my own convenience
any progress on this one so far?
so i got someone to help me and for a) i got 27017.7 b) idk yet
can you tell me how you got 27017.7?
so since 1 revolution is 2pi radians and there are 4300 revolutions per minute, it should be 8600pi rad/min
ye then i simlified it
you put it in a calculator.
i wouldn't call that simplification.
you were asked to round to 2dp and you did.
... might wanna go to a help channel or wait
@ripe siren ok so now you want to find the linear speed of a point at the edge of your saw
do you know in general the relationship between angular speed and linear speed for circular motion?
yes/no
(no numbers yet!)
yes as the angular speed increase linear speed increase, no?
that's too vague
do you know how to calculate linear speed given angular speed and radius?
no i do not
right ok in that case
srry i dont kow much math
let's step back a bit
since there's something we need to go over
instead of speeds let's talk about lengths first
so you know what a radian is, yes?
(yes i'm going somewhere with this, i just want to explain things fully before we get back to your problem)
thank you for trying so hard to try to explain it to me but i got the answer right 🙂
sorry i cut u off like that
:((
i didnt mean to waste ur time
bruh
im soo sorrryy
genuinely
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)
no, sorry that it :((
yo do u think u could help me now possibly
no guarantees
but deezniks and i appear to be done, so you can post your problem (in full) now
i need to use the function in the rectangular coordinate system
which is pretty easy to get the mins/maxes
would i just use the rectangular coordinate system again?
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.
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.
that's what i said, yes
alright thank you so much i appreciate the help
Anyone here good with angle of rotation?
!da2a
No need to ask “Can I ask…?” or “Does anyone know about…?”—it’s faster for everyone if you just ask your question! See https://dontasktoask.com/
Is that Yamato?
Yeah
Find the angle of rotation for 13x^2+6sqrt(3)xy+7y^2-32=0
Bro
I got cot(2theta) = 1/sqrt3
Is that even precalculus?
It is
Sqrt????
Is it possible for me to transfer 2 to the other side?
Square root
Im in college
Thank God.
2nd year 1st sem
Alright so I am safe fore a few years
Angle of rotation as in those idk transformations?
Wdym
a few prob means 2 buddy
Nah, 5
how old are u
11
oh hell nah
oh nice im 16
Am in grade 9
oh really?
☠️
You in grade 10?
11
Nice
im not too sure about these grade things
Ohh shit, imma be 16 when I finish 10
cus i learnt the stuff youre learning when i was 14
how do you find derivatives of functions
This calculus 1 video tutorial provides a basic introduction into derivatives.
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...
This calculus video tutorial provides a basic introduction into the definition of the derivative formula in the form of a difference quotient with limits. It explains how to find the derivative of a function using the limit process. This video contains plenty of examples and practice problems.
Derivatives - Fast Review:
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This calculus video tutorial provides a basic introduction into derivatives for beginners. Here is a list of topics:
Derivatives - Fast Review: https://www.youtube.com/watch?v=5yfh5cf4-0w&t=1s
Limit Definition of the Derivative:
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Derivatives - Alternate Limit Definition: ...
Finding the slope of a tangent line to a curve (the derivative). Introduction to Calculus.
Watch the next lesson: https://www.khanacademy.org/math/differential-calculus/taking-derivatives/derivative_intro/v/calculus-derivatives-2?utm_source=YT&utm_medium=Desc&utm_campaign=DifferentialCalculus
Missed the previous lesson?
https://www.khanacadem...
@queen shoal here, you might wanna give these a watch to start with.
do you have a specific function you want to differentiate
if so I can walk you through it
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
Does anyone know how to do these number 6,7,9,11,12
Yes
Wait what
No
I'm in algebra 1, i just am learning this stuff
but what are integrals? and what are derivatives?
and what are hyperbolic sine/cosine/tangent
you shouldn't worry about this in algebra 1
no i should because half of my class is foreshadowing for this
and its like
what you're learning is baby math
compared to
[insert trig or other stuff like calculus]
almost all math is baby math compared to something. but math builds on itself, so you have to have a solid foundation
well the simple explanation isn't going to be useful and proper explanation isn't going to be short
then you can just open a book/search the web/watch a lecture on it
i did
but
I need somebody to personify it
because i dont understand what they say
this is why you learn basic stuff first
you're not going to find a lot of people that are willing to explain material for hours
true
so it would be better if you have specific questions about stuff you don't understand
alright
is altitude easier to explain?
because i need to know all of this for math olympiad
and im in 6th
altitude?
so idk any of this
sure
so how would i do it?
draw a straight line from vertex B to the side AC
does the angle have to be a right though?
because then
if it isn't it can be anything
what angle exactly
if the point we are drawing from B to is named E
the vertex can have any angle, the altitude always creates a right angle with the side it touches
then BEC
ok
makes sense
none of the resources i found said that
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...
and it says it right there
my browser is broken
,w rref {{5,-3,2,2},{2,2,-3,3},{-1,7,-8,4}}
it's not inconsistent, but it does have infinitely many solutions
rewrite this back into a system of equations
then you can solve for x and y
can i??
just move the z term to the other side on each side
then you have a formula for x and y in terms of z
but thats in terms of z then
yes, that's why there are infinitely many solutions
so
each value of z corresponds to a different solution
not sure how to properly turn this into a system of equations
find the number of beef required to produce some amount of muffins, bones and cookies
ohhh wow that's really really helpful thanks
oh shit wait
sorry
i thought that was a sarcastic message until i reread it and you were unironically being helpful sorry 💀
...i still do need a little more help though given that im stupid
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
then do this
so, what would each variable be representing here
the number of muffins, bones and cookies produced 👆
Thanks
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
what is “most of it”? show us what work you have
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
Wait I do actually
Greatness can be attained through rigorous exercise.
Though this is quite a difficult math
Is it related to functions?
it's introductory linear algebra
College level?
linear algebra is usually taught at the college level, although some high schools teach a small amount as part of an algebra/precalculus curriculum
the derivative of the function: ln(f(x)) is generally f'(x)/f(x)
... which is just a particular case of the chain rule.
this requires a bit of something called "chain rule"
are you familiar with derivative rules @queen shoal
ok well that's a pretty tough derivative for someone who's never done derivatives before
i dont know chain rule either
i'd recommend learning the basics first
ok
what are the basics
it's either a "complicated" algebra 2 problem or a "basic" linear algebra problem
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
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?
it's multiplied by n
make sure you aren't getting it confused with the antiderivative
True lol. But then, why is it multiplied by n?
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
use the limit definition of derivative, and use binomial theorem for (x + h)^n
hi
Someone tagged me?
here mebbe?
Nah nah someone else
Thx
The hint is very useful about negative numbers
Is your problem with how to get the domain or writing it in the given notation?
Getting the domain
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)"
do you mean "I don't know what you mean when you say sqrt(x)" or do you mean "I don't know the domain of sqrt(x)"?
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
No
It sounds familiar, but i couldnt tell u what mx or c is from
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...
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: ...
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.
I did it y’all
I got into ap precalc
The 2 weeks of staying up until midnight was worth it
ayy
chat gpt actually made a mistake??? 🤣
unless it was talking about limits
then you ignore that kind of domain restriction
idk tho
yep I asked it to help me simplify and it say'd that -64=-8
well cuz it canseled out x-64 and x-8 meaning their the same and also implying that -8=-64
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 💀
lol
I was just expressing my rage over AP Pre-Calc 😞
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!
no literally thats why i transferred out of precalc in the first two days lol
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
if a class taught calculus it would be called a calculus class...
Exactly! I’m taking it over the summer since I basically know all the material, I don’t wanna spend an entire school year reviewing stuff I already know..
AP Precalculus should at least introduce the topics in the first 2 units of Calc AB/BC or else what difference does it really make?
i think they teach basic limits sometimes in precalc
I thought they did…but they don’t even talk about it in the AP 😭
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"
I already know limits too…
i remember i looked at the syllabus for precalc and i was like "bruh i thought this was algebra"
Yeah, a regular Precalculus course. If the AP just teaches the same stuff and doesn’t even slightly delve in Calc AB stuff, then what makes it different?
i thought precalc was matrices, polar coordinates, conic sections mebbe, vectors, limits, probability? idk
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
The AP exam doesn’t cover matrices, vectors or limits
But AP Precalc doesn’t even give you credit at most colleges given that Precalculus is a high-school course
AP classes are typically either the first semester, or the first-year of a college course
most colleges do offer a precalculus course for students who do not yet have the pre-requisite knowledge for a first-year calculus course
Yeah, but again, most colleges won’t give you credit for AP Precalc given that as you said, it’s only taken for those who don’t have the prerequisite
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
I suppose sure, but I’m just saying, there’s nothing that makes it “college-level” like an AP course is supposed to be
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
Not straight-up teach Calculus, but introduce some of the topics at a slightly more basic level perhaps. Cause like I said, AP Pre-Calc doesn’t even cover matrices, vectors, or “functions involving parameters”
And those topics are not that difficult, at a Precalculus level, matrices are super easy to wrap your head around
@steep estuary
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
Ap calculus?
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?
calculus is barely scratching the surface of actual undergraduate mathematics
i think calc 1 is where undergraudate starts
which would technically be 'college level'
How do you scratch undergrad maths from both ends?
what does that even mean 🤣
the meatier parts of the undergrad curriculum begin when you start to move away from just endless computation and move towards proof-based stuff
Ahh I just love smth that's meaty like proof.
I tried proof, understood some of it, but like it's quite conceptual I felt.
the most important undergrad courses are probably abstract algebra and analysis
.... that is a completely vacuous statement
some undergrads take it
Ahh I see
the point of undergrad is more to
develop the mathematical maturity you need for intensive graduate level research
No it's a standard upper undergrad course for pure maths
I probably won't even be picking maths in undergrad since I am going into bio but still it's quite interesting.
Cool
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*
Oh, all you have to do for me is to get an C or higher in AP Pre-Calc, or an A in regular with a teacher recommendation. And that’s for BC, it’s even more lenient for AB
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
pnoןɔ
I still dont understand it
,tex \exprules
pnoןɔ
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)
Whoa, are there cmds for other types of formulas aswell?
you need preamble for that
any one help me i have high school additional math exam in this year
post the question(s) that you need help with
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
$a^x = e^{(\ln a) x}$ and the chain rule
south
Trig and functions
Like logs, exponential functions, rational functions, sin, cos, tan etc
Usually if i have smth regarding to trig, i go to trigonometry channel
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
😧😧😧😧
give us a picture.
So high.......
Bad joke mb.
wat
,, \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.
milanesa de pollo
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 $\lim_{x \to +\infty} \left( \frac{\sqrt{ax^4 + bx^3}}{x} - x \right) = 4$.
|Ann⟩
also show all your progress thus far.
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
no, it's much better than leaving the status query on read.
for step 1 i suggest rewriting this thing as a single fraction
then you can do some bullshit with conjugates.
Take x^4 common
From root
That would give x^2
Take both x^2 common
And cut one x
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
not any more so than any other limit with roots like this.
It's useful when tending towards 0
I dont get it
trust me it is still helpful here
mb because two people are trying to tell you different things
and so high is doing it in a somewhat hard to read way
i have to go sleep tho so maybe it will have to be the blind leading the blind
take x suare common
a has to be 1
why?
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
I had 0 context before seeing you say that, so for a moment I thought you were saying that calculus sucks, lol
i made it myself, so you can get such commands by making them
what’s the formula for an alternating series like this? i cannot remember lol
alternating geometric series don't have a separate formula from other types of geometric series
lets talk tomorro
a/(1-r)
1/5
1/26 is tat the ans
ok ty!
oh that’s an s not a 5
oh my fucking gad
!nosols
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.
this is still a geometric series
$\frac{(-1)^n}{s^{2n+2}} = \frac{1}{s^2} \cdot \paren{-\frac{1}{s^2}}^n$
|Ann⟩
Represent the following sets on the line. Write them as intervals or as a union of intervals
${ x \in \mathbb{R} \mid |x| > 3 }$
milanesa de pollo
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
yeah
well
|x| > 3 means x is further than 3 units from 0
this should enable you to draw it on the number line
-3 > x > 3 maybe?
so strange smh
but I only know because if |x| < 3 then -3 < x < 3
no
then prolly |x|>3 means -3 > x > 3
i said draw on the number line
no, stop trying to mash symbols together
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
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.
That was the lesson learnt that the two side inequality is wrong
How to write that as union of intervals?
not sure
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.
two
right.
let's look at the first interval, on the left.
how do you write this in interval notation?
not sure if the ifinity is inclusive but
(-infty , -3) would be my guess, since you cannot include infinity
you never include infinities.
but yes, (-∞, -3) is correct.
now look at the second interval, on the right.
what's that in interval notation?
(3, +infty)
right.
,tex \exprules
How do you make em?
read the pins in #latex-help for a more general introduction to latex
how can I graph $f(x) = cos(2x + \pi)$ just from knowing how to graph $g(x) = sin(x)$ and $h(x) = cos(x)$
?
@proven void
wassup
What's senx
milanesa de pollo
typo, mybad
,w plot cos(2x)
how do I flip it
nah
I thought u meant on paper
Like for general understanding
Do u know how to plot cos2x=
no
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
how do I
anyway
cos2(x+π/2)
?
2cos^2(x+π/2)-1
Im checking it for myself
I don't see the use of sinx graph in this
Also
meh
Well I hope u understand the graph
how to I sketch cos(x) ?
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
$\lim_{x \to 0} \frac{(16+x)^{1/4} - \frac{1}{32}x - 2}{x^2}$
|Ann⟩
i think i'd rather wait for OP to give confirmation that i have the problem written correctly
@near sentinel
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.
|Ann⟩
failing that (such as if op doesn't have access to taylor series), we could resort to l'hôpital's rule.
what are the conditions that need to be met so lhopitals is possible to be used?
2^4 = 16 I didnt noticed
taylor series?
i mean, by asking this question you admit to not knowing what l'hôpital's rule is.
but the most important condition is that the limit is in either of the two forms 0/0 or ∞/∞.
here it is 0/0.
oh yeah its 0 numerator as well didnt noticed, again 2^4 = 16
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.
$(1+x)^p = 1 + px + \frac{p(p-1)}{2!} x^2 + \frac{p(p-1)(p-2)}{3!} x^3 + \dots$
|Ann⟩
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)
was tough to see at first glance, but this is covered in two weeks for me
whats next?
yupp
ok then i repeat my suggestion:
yeah
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.
here's what I did, I rationalised the numerator and got until {16+x - (x/32 +2)^2]/32x^2
idk both of these 🫠
wait whats power series
can you show your work for rationalization
i think ik it but with a dff name
sure
then that is what i meant
ohkk
my teacher did teach us aa method uding binomial expansion, but im not very good at it
yeah binomial expansion is exactly what i am suggesting here.
$(1+x)^p = 1 + px + \frac{p(p-1)}{2!} x^2 + \dots$
|Ann⟩
explain what
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
rewrite $(16+x)^{1/4}$ as $2(1 + \tfrac{1}{16}x)^{1/4}$ and then as $$2 \paren{1 + \frac{1}{4} \cdot \frac{x}{16} + \frac{\frac14 \cdot (-\frac34)}{2} \cdot \paren{\frac{x}{16}}^2}$$
|Ann⟩
you are not expanding far enough
you need the x^2 term from the expansion too
ohkk
ill try doing that
thank you!!
that way there will remain a term of x in the denominator
this is what im getting
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
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
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
nope 😦
yeah, it only works till 3rd term, we were told to ignore the rest of them as it approaches to zero
💀
exactly, and even the ans is coming diff
@willow bear , any idea?
its actually a build up question
ill send the prev q
like its implied you have to solve it like the prev question
did you rationalized for 3?
or binomial expansion/ taylor series around x = 0
?
why is 4 repeated twice
but with different functions
thats a diff question, its like a hw assignment and our sir is too lazy to change index
yupp
i got the answer for 3
by rationalisation
but im supposed to do it by binomial exp
and the ans comes either way
,w lim[x -> 0] x^-2 * ( (16+x)^(1/4) - x/32 - 2)
💀
did your prof proclaim that the answer is positive?
really nice question tho
or the ans key
yeahh
whatever
What to do?
