#precalculus
1 messages ยท Page 195 of 1
@pale bison no

do u get what
what you wrote on the very left is $x^{\sqrt{2}}$
im thinking
Ann:
if $x \geq 0$, then $\sqrt{x^2} = x$.
if $x < 0$, then $\sqrt{x^2} = -x$.
Ann:
@trim fable
i wrote everything.
and?
if $x \geq 0$, then $\sqrt{x^2} = x$.
if $x < 0$, then $\sqrt{x^2} = -x$.
this requires no further comments.
every number would be
Ann:
$\sqrt{x^2} = |x|$ literally by definition.
Ann:
do you understand this or not.
no
i literally just explained it
ok
ok..
if $x \geq 0$, then $\sqrt{x^2} = x$.
Ann:
do you understand this or not
is it true that $-5 \geq 0$?
its not (-5)^2?
Ann:
no
no, it is not true that $-5 \geq 0$.
Ann:
lol
if $x < 0$, then $\sqrt{x^2} = -x$.
Ann:
do you understand this or not
yes?
but u wont answer my question
u wont square the negative with the number
just the number?
your question makes no sense
so its technically - (5)^2 = -25 not (-5)^2=25?
if the number is -5 for example
its not (-5)^2?
what's it?
what's "it"?
what's "it"?
what's "it"?
the answer
what answer
YOU'RE NOT MAKING ANY SENSE.
of rip
WHAT EXPRESSION.
x^2 when x= -5 apparently
IF $x = -5$, THEN $x^2 = (-5)^2$.
Ann:
but what i was saying was
no stop
ok
there are exactly two real numbers which when squared give x^2
x and -x
do you understand this or not
oh ok
for any given value of x, sqrt(x^2) will by definition have to be one of these values.
it will be precisely the one of these values that is positive.
do you understand this or not.
yes
okay.
what im saying is it will ALWAYS BE + ?
I'M NOT DONE YET.
when x is positive, -x is negative, and therefore sqrt(x^2) = x.
do you understand this or not.
when x is negative, -x is positive, and therefore sqrt(x^2) = -x.
when x is negative, -x is positive.
well what i was questioning actually
do you disagree with this?
(-x)^2 is positive
when x is negative, -x is positive. do you disagree with this?
i am expecting one of two answers:
"yes, i disagree with this" or "no, i agree with this"
no
?
i agree?
u mean the final
answer
when u say -x right?
like after u square?
for any given value of x, sqrt(x^2) will by definition have to be one of x and -x.
it will be precisely the one of these values that is positive.
when x is negative, -x is positive.
therefore, when x is negative, sqrt(x^2) = -x.
what part of what i just wrote is confusing?
i was under the impression that the entire argument was laid out crystal clear
and that i "meant" exactly what i said
lmao
what the fuck do you have to say now
no
no
you aren't squaring x there
if x = -5, then x^2 is NOT -5^2
(-5)^2
because ORDER OF OPERATIONS is a thing no matter how much you wish to forget about it

what you were saying made very little sense if indeed it made any sense at all.
no
were u
i did not
talking about
The final answer????
ohhhhhh ripppppppppp
omggggggggg
what was i thinkinggggggggggg
i thought u meant
bruh
if by "the final answer" you mean "the value of sqrt(x^2)"
that was basically expanding the |x|
OMGG
THEN YES OF FUCKING COURSE THAT IS WHAT I WAS TALKING ABOUT
wot m8

coz ur squaring itttt
what the fuck are you saying
what
so i started questioning u
hi ann
whut?
are we in hell again today
the x is clearly negative in the second case as stated by "x < 0"
its absolute wow
you mean the square root?
no LOOK
yes that is always positive
YES
JUST BECAUSE A MINUS SIGN APPEARS IN FRONT OF A VARIABLE
DOESN'T MEAN THE VARIABLE ITSELF "IS NEGATIVE"
i thought he meant after squaring u got a - coz i thought he was doing
if x is positive, then +x is positive
who's he
i'm a she
k
aight
Damn
okaaay

no u
no u
Why?
u were right but i was too
You have nothing to apologize for
hhh
Just learn as much as possible and move on.
i feel like i lost a few thousand think pan cells from this
oh no..
IM SORRY
gives u my brain cells
tho idk if
u want them
they are pretty useless it wont
make a difference
lol
it's ok you can keep them
Ann, you worked yourself up over something like this.
Anyways, Star, just try to understand what Flynn and Ann were telling you before
are there still parts you aren't sure about?
i just thought they meant something else
ohh
tho the final answer in the end was
agreeable
i guess
ye so
are u all mad at me ;-;
It's okay. There was no reason for them to work themselves up like that.
sorry guys
There's no reason to be mad at you.
Like what ramonov asked, is there anything you're unsure about?
jesus christ
Alright.
There's no reason for ANYONE here to get irritated just because you're asking questions.
there u got the english u wanted @fluid shore
just don't use freshman's dream again
what do u mean @uncut mulch
this is math related
math related emotions
EVERYONE
there lol
earlier you implied that the sqrt was linear
ME?
yes
oh rip when
sqrt(x^2 - 2) โ x - sqrt(2)
Idk lol, it's a term that some of them use for some incorrect stuff
Anywyas, if you're stuck on something, just ask questions.
in general yes this is false
ok
freshman's dream is sth different
sth?
something
oh
,w graph y = x
how many freshman's dream are there,
are there an undergrad's dream?
freshman's dream is $(x+y)^p \overset{?!}= x^p + y^p$
,w graph y = abs x
huh
Just wanted to give you a visual image of it.
yes
freshman's dream is $(x+y)^p \overset{?!}= x^p + y^p$, for $p \neq 1$. most often encountered with $p = 2, 3, \frac12, -1$.
what
Well, that's usually a good thing to do but making mistakes is absolutely fine.
Ann:
im in grade 12 and im making dumb mistakes like that
thats honestly pretty sad
tho i am good at it i just do random stuff at timed
Well, then, try not to make such mistakes in the future
If you want to learn this stuff in greater detail, i'd suggest using something like brilliant.org
ok
Use the wikis there to learn the material and solve problems there as well.
ok
abhijeet is the brand ambassador for brilliant
๐ฎ
Well, I think it's a fantastic resource.
did someone mentioned brillian.org, our sponsor for todays video
^
honestly, i'm like iffy on what brillian's doing in terms of building their own wiki page
an entire class of fuckups
just doesn't seem right to copy off wikipidia
ann how could you interrupt the part where we thank our sponsors
Oh they don't, from what i've used anyways. The wikis are made mostly by olympiad students who've learned the material from other sources
use code im total sellout to get 10% off your first month of purchase
Now, it has branched away from olympiad material
if they're sponsoring us, they're not doing a very good job
just in case Wikipedia goes down, but that will never happen because you have donated 
true
lmao
well we could technically download all of wikipedia onto an external drive at this point
I've contributed to their physics wikis before but that was at a time when my understanding of physics was very limited.
there's a chinese wiki called ็พๅบฆ็พ็ง
I just don't understand why this devolved into such a massive fight. I don't even understand how it got linked in chill.
But whatever
what fight?
what fight
baidu wiki?

well yeah i merely mentioned it
baidu-pedia i guess
i don't see a problem
็พ is like, the hanzi for ๐ฏ or sth
i'm suggesting that in the very unlikely of wikipidia going down, there's a chinese one
20 years living in singapore and i still can't speak chinese or even read it
it means one hundred
I've heard it's a pain in the ass to learn
hundred
i agree
TIL
I thought it was 100 horizontal lines
how do you explain that ็ฝ means "white" then?
lmao
what
็พ means 100
็ฝ means white
chill... i'm just responding to his message
$\dv{็ฝ} $
DarK:
้จ is the best looking character imho
็จ
่ตข
ใๆฏใฏๅคชใฃใฆใใพใ
Could anyone explain how to solve so the variables become the above?
I basically put them both on the same fraction, multiplying A with xยฒ+x+1 and Bx+c with x-1
Then I take out the X's, everything in the brackets of Xยฒ(...) should be 0
same for X(...)
and the rest is equal to 1
But that doesn't work at all
In other words, we compare coefficients and get A, B & C
But that doesn't work at all
wdym
you're on the right track so far, based on what you've said
what exactly does not work
-A+B+C = 0
,w expand a(x^2 + x + 1) + (bx+c)(x-1)
oh
$ a(x^2 + x + 1) + (bx+c)(x-1) = ax^2 + ax + a + bx^2 - bx + cx - c$
Ann:
$= (a+b)x^2 + (a-b+c)x + (a - c)$
Ann:
General question out of curiosity:
If I take the derivative of the integral of some function f(x), then I would get f(x), right?
But if this integral is definite, with x going from a to b, is the derivative of the integral of f(x) equal to f(b)-f(a)?
it would be easier for you to check this yourself than to ask
but also think about what do you really mean when you as kthat question
is it coherent?
I'm not sure what you mean by that, English isn't my first language
Well first, functions that look like
$$x\mapsto\int_a^xf(t)\dd t$$
aren't always differentiable everywhere, so even your first question should be answered negatively I suppose
Tuong:
Oh yeah, true
Perhaps in the example of the derivative of the definite integral of (cos(xยฒ)) with x going from a->b
you can even have differentiable functions that look like
$$x\mapsto\int_a^xf(t)\dd t$$
but which derivative isn't equal to $f$
Tuong:
for your second question, you're asking about the derivative of the number $\int_a^bf(t)\dd t$
\ \
if you identify the number with the constant function, then its derivative is $0$
Tuong:
Right, that makes sense
If I could ask one more thing, say we introduce a second variable, like so:
d(integral a->x of cos(tยฒ)dt)/dx
If that's readable
What would this give us?
I can't really calculate the integral first, that's my biggest issue
Thanks for the clear explanation by the way
there's a theorem
basically with continuous functions everything works fine
if $f$ is continuous then $F:x\mapsto\int_a^xf$ is differentiable and $F'=f$
Tuong:
Oh right, that would work with what you said earlier (my second question)
Perfect, very much appreciated
You're welcome
@odd helm I dont see any equation
"50 dollars per piece" means you need to multiply the number of pieces by 50
i think he's trying to describe a profit function
if the starting price is 50, and you are projected to sell 4,500 units, then you're equation looks right
im no sure what they are doing
It is 50 dollar per piece= 4500 items sold
Every dollar increase means 5 less items sold
Oh
im not sure what they are doing tho
im really lost on what they are doing
oh i got it
they are doing it by actual price
not increase like you did
yeah same thing
Alright
Whatโs the difference
And whatโs the use of a dx in the end of a integral
Ok so if I solve both those equestions whatโs the answer for both
how much integration have you done?
Like none
then the answers we give will probs be meaningless to you
Is it possible to answer the second one
So whatโs the answer
how much calculus have you done?
Fuck off
Ok this is true right?
Well I have to add the d theta in the end
But this means that the d whatever is the same as taking the derivative
Yo someone answer
$\int \sin\theta \ d\sin\theta = \frac{\sin^2\theta}{2} + c$
FlynnXD:
$\int \sin\theta \ d\theta = -\cos\theta + c$
FlynnXD:
$dy = \bigg(\frac{dy} {dx}\bigg) dx $
FlynnXD:
that's not correct though
I think there's a - missing too
^
because the integrand isn't in terms of the thing you're integrating with respect to,
and you'll need to do some maniuplation
i mean you could try, but you'll still be left with dx
it just depends on whether it simplifies your problem or not
in case of sinx d(sinx) it actually is easier to evaluate
i reworded what i posted earlier
you can play around with the d(..) in many ways
that's basically the whole u-sub thing
the integrand here x^2 is in terms of x so manipulation of the differential isn't needed
Cool that was helpful
@hallow flicker you're doing integrals in precalc?
gnarly scope creep
Iโm doing ur mom dude
Rekt
$\mathbb{R} e^{k} \dagger$
A. S.:
OOOOOOOOOOOOOOO
ur mom is applicable in nearly every situation
Oh shit rekt
Can anyone help me with this?
do you know your unit circle?
what's giving you trouble here? @radiant night
Well I know how to use the unit circle, but one wasnt provided since its sub work.
And I need the theta= aswell, since it's been a while since I've done that,
Well I know how to use the unit circle, but one wasnt provided since its sub work.
you're supposed to be able to reproduce it from scratch
Well, we've only learned it a couple times, and I dont have the greatest memory.
memorize it, or memorize the special right triangles
^ do you at least understand the first quadrant
you only need to memorize the first quadrant
the rest is the same but just use sin cos rules in different quadrants
A S T C
I dont have the greatest memory
You have google for that
||luckily we have a formula book for all formulas in hs math||
i'd say don't memorize but i don't have enough energy rn
The basic trig values have easy to remember patterns. (root 1)/2, (root 2)/2 and (root 3)/2 for (co)-sines. And (root 3)^1 /3, (root 3)^2 /3 and (root 3)^3 /3 for tan.
Well you only need to memorize first quadrant
And then if you can draw the triangles on the axis
You're good
Because the unit circle lies on the xy plane
So
If the triangle is in the 2nd quadrant
You know that the cosine (which lies is the x-axis) is negative because in the 2nd quadrant x is negative
Cause it goes to the left, and in the plane we define left of zero as negative
What do you think?
1/x^2-1
No, thatโs not the answer to my question.
oh
My question was: what do you think is the approach to be taken?
oh
so take 1/x^2-1 and plug in f into x
which gives u 1/(1/x)^2-1
and then 1/1/x^2-1
Since itโs g(f(x)), shouldnโt you be plugging in f(x) into g(x)?
thats what i did?
What you did was f(g(x))
Oh wait nvm, i misinterpreted your working
oh sorry
Ann:
Yea yea lmao
oh oops
Use latex to type this stuff out, star
$\frac{1}{(\frac{1}{x})^2 - 1}$
Abhijeet Vats:
Thatโs what you were going for?
yeah
Aight, then simplify
A brief description and guide on how to use me was sent to your DMs! Please use ,list to see a list of all my commands, and ,help cmd to get detailed help on a command!
Uhhhhhhhhhhh
c ii looks wrong
Itโs late here and iโm tired but it just seems wrong, given what you had earlier
yes you did
yes c i is right
$\frac{1}{(\frac{1}{x})^2 - 1}$
Abhijeet Vats:
Simplify this properly
ok
The feeling when u think ci and cii are related and some higher math
Tired, perhaps
Can I ask my questions
Zoom in lmao
I can provide some insights on question 6
For question 6, consider the periodicity of the trig functions.
And compare it with the average rate of change
Sin, cos and tan will have an average rate of change equal to zero
Now consider the inverse trig functions
arcsin and arccos are not defined when given an input 2pi so discard those
arctan(2pi) - arctan(0) = some number greater than zero (calculator)
So discard arctan
โ
Now youโll need to test the hyperbolic function and their inverse
Which Iโm too lazy to do
How do you make a rational function with an extraneous solution?
Hi
is that a typo in the second line in the answer section
question says csc > theta
no
then sec theta is positive?
the question says csc(ฮธ) > 0 not "csc > ฮธ"
yes i meant that
but in the answer section is that sec ฮธ is positive?
that's a typo i think...
anyway yeah it's a typo and they meant csc and not sec
it's been 4 days already lmao
hahahaha
I didnt know where to ask ๐
Explain
We need to solve log 9 approximately
?!?
Yes base 10 log
Nvm i got it
hey guys! i have a math problem i have been stumped on for an hour

so it shows me the answer is -7/-3
but i cannot get to that answer no matter how hard i try lol
ill send my "work" in a second
does it show how to get the steps
pearson socks?
,w vertex of 3x^2+8x+3
so, have you ever done finding the vertex of a parabola before?
show us your step by step work
^
that 16/3 is negative
You should really leave a blank line between each statement in your working.
ah i would subtract the 16/3 from 3
^What you do or don't isn't the point. It's neat to do it that way.
then again I write stuff like $\forall a \exists b \phi_a(b)\implies \psi(c)\vdash \forall a \eta(a)$
Darkrifts:
also yes goon
(note: ignore the thing I wrote above, it's a meaningless example of why you shouldn't write like me)
that looks a lot like the right answer
haha awesome i was improperly messing with the faction and whole number
thank you! glad i found this discord
$y=2\arctan{\frac{x+1}{3}}$
Umma.Gumma:
$x=3\tan{\frac{y}{2}}-1$
Umma.Gumma:
I had to find the inverse of the first function, which is the second one, no problem about that. The thing is I have to determine the domain of the inverse function as well
given that there's a tangent I would be tempted to say that all values of y are valid except -pi/2 and pi/2
however it seems that the correct domain is $y\neq\pi+2k\pi$
Umma.Gumma:
can anyone explain this?
Well when does y/2 take a value that is a integer multiple of pi/2
an ODD integer multiple of pi/2
Iโm having some sort of brain fart. How is (1+x^2)^1/2 * (1+x^2) = (1+x^2)^3/2. Where is the ^2 exponent thatโs being added coming from.
Or is it (1+x^2)^2+ ^1/2.
That might be it. Nvm.
@desert socket (1+x^2) = (1+x^2)^1
and then it's exponent rules
a^b * a^c = a^(b+c)
I got it. Thanks!
lol i have someone making me second guess myself
the answer to that should be 3 right
yea
ok thats what i was thinking lol caught it on a peer review and had another friend explaining some crazy shit making me second guess myself
is that the whole question that u posted @proud jetty
yes
unit is permutations and combinations. every letter have a different answer, u gotta solve for it.(not a multiple choice question)
how do i do "how many code words of any length can be spelled out using gmae timles of five different litters ( including single lettered words)
also how do you do
expansioin of polynomials byeond binomial
can anyone help me please
uh
wtf is gmae timles
^
yeah
well I assume the "words" don't have to make sense
yeah i dont think so
just random permutations of the letters
what's your difficulty then
minimum length is 1, max is 5, take each case and figure the number of possible words
oh i did that but looking back i realized what i did wrong
i used the wrong amount
coluld you also help explain how i do expansion of a polynomial that is greator than a bionomial
what does that even mean
so binoimal expansion is when its like this (x+1) (y+1)
but im talking about something like a tri nomial
so with three of those
yeah but how would i distribute through with a short cut method
In mathematics, the multinomial theorem describes how to expand a power of a sum in terms of powers of the terms in that sum. It is the generalization of the binomial theorem from binomials to multinomials.
thanks
not sure if that's what you're asking for, but check it out anyways
we derived this in hs, cool stuff
cool thanks
i think i also realized that for my school we used something called lines and stars method
its k9inda weird but it works
yeah I remember that one
@viscid thistle 
it's g o o d p r a c t i c e tho
paku dropped a question here and went offline presumably to wait until the answer is handed to them
hopefully they went to find a book that explains how parentheses work
This is a misprint too, right?
yes
3 misprints on one page. They've gotta be shitting right into my soul.
For computers, what base is the log function set to by default?
wdym by "for computers"
2
uh
no
first off it's likely not 2
and second you really have to ask your programming language's documentation
not us
:d
Well, suppose $log_{10} x = y$
Abhijeet Vats:
Then, you agree that:
$x = 10^y$
Abhijeet Vats:
?
No. $x = 10^y$, correct?
Abhijeet Vats:
oh
What did we define y as, initially?
Nope
$a^x = y \iff x = \log_{a} y$
Abhijeet Vats:
That's how you get logarithms
yeah im not good at logsss ahhhh
With some restrictions on what a is and y is, of course.
they confuse melol
yeah
well i have another question
about domain and range
brb tho
one sec
Try them on your own first
i did
i solved for them all
but now just have to do
domain and range and i did it for the first two but
do i use the graph method?
where u draw them out
and set the y and restrict
idk it was confusing i learned it today
Nope, you can do it analytically for all of them. You don't need to draw the graphs, though it will be good practise for you if you do draw them out.
oh
so i cant just look at it and
state them?
oh also for example
like one of the examples was
f(x)=x+3 and g(x)=x^2-12
so then what we did was drew g(x) looked at the range and then
Why not just write things down?
??
?
Do you know what composition of two functions is?
yeah
f(g(x))
but then why are u using g(x) first
when its the inner one?
inner then outer function?
for these?
What do you mean 'why are u using g(x) first'?
Why are you drawing them/
and taking its range
?
Why are you drawing them?
told us
to draw
them
tho its
confusing
is there a different way to
state domain and range
without having to draw and then
use the range as the domain for f(x)
and then finding it
to see if its valid
Like I said, you can determine it analytically for the given functions. You don't have to draw the individual functions, though it's good practice.
You should actually just google these things. They're not that hard to learn online. Once you have learned them, apply them to your problems and then come back here if you're stuck.
Well, google the composition of functions and how to determine the range/domain of a composite function. They'll give you a whole bunch of results.
Work through the examples you find, then work through your teacher's examples. Then, come back here if you're stuck with an actual step in your working
of composites ok thats what i meant
ok
yeah i calculated f(g(x)) and g(f(x))
for all and checked the answrs and got them but
i dd the domain and range for the first 2
tho idk how to do c
coz u get
sqrt(4-x^4)
Okay then?