#help-43
1 messages · Page 14 of 1
but since the top absolute value is multiplied by -1 would i take that -24 and make it positive?
That is wrong
i see that
I get something else
I see that you guys went over that |x^2-10x|=-(x^2-10x) for this particular limit
That’s what I got
ptrobably something wrong with the numerator one
,w when is (60-6x-|x^2-10x|)/(|x^2-100|-64)=(60+4x-x^2)/(36-x^2)
?
i think i know
let me cook
it was the negative before the absolute value
@eternal pulsar
i just cooked
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am i right with D here?
please show your work
i would but its on paper
✅
THANK YOUUU
If it's correct, why must they show their work?
to confirm they did it right
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hi can someone please explain what “coordinate of the Cartesian vector” actually means? Like the coordinate is the change in x and y, so [2,-5] but what exactly does the 2 and -5 mean? Im new to Cartesian vectors so im a bit confused by the notations
when split into x and y components
could also be considered displacement from point A if you want
so then in order to convert a cartesian vector into coordinates, we always do tail - tip for both x and ys?
well you need an origin to start from since it isn't defined by the vector directly
but pretty much
what does this mean btw
also if you're just given the coordinates [2,-5] is there an infinite amount of equivalent vectors that could be drawn?
like you don't know from the vector (2, -5) that it starts at A
aa i see
technically yes, since a vector is just direction based no matter where you draw it it will always have the same direction
but typically they are drawn at the origin
0,0
sure
how do i convert a vector into a unit vector?
like
for example
given vector v = [5,-1], how do i express it as 2 unit vectors that are collinear with v
have you seen the formula $\hat{v} = \frac{1}{|v|} \cdot v$
BuilderDolphin
yup, tho i dont really understand what it truly means behind the symbols if that makes sense 😹
lke what does it mean exactly when we express a vector as a unit vefctor
a unit vector is a vector with magnitude 1
sort of related to the unit circle
r = 1
yea that makles sense, but what does it mean if we rewrite v as a unit vector
it means we divide v by its magnitude, resulting in unit vector v with magnitude 1
$\hat{v}\cdot |v| = v$
BuilderDolphin
unit vector v is colinear with v
huhhhhhhhhhhhhhhhhhhhhh
i should probably clarify |v| means magnitude
if that was confusing
$\hat{v}$ is just saying the unit vector v
BuilderDolphin
what seems to be the confusion
i can reexplain if needed
why does it give you v tho
(mightve gone too fast)
OH
wait is it because
v with funy hat is magnitude 1
so that times magnitude v = v
ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
uhh
so like
they got some very funny thing
they got
[5/sqrt26, -1/sqrt26] and [-5/sqrt26, 1/sqrt26]
uh what was the problem with those
so i dont get like
how you get them
and im kinda confused again on what it means
well you have this equation
can be rearranged to this
which is more practical to use
so basically each time we just do the 1/magnitude * x , 1/magnitude * y?
magnitude like length right
correct
You can alternatively say x/magnitude and y/magnitude
||Just to avoid any notational confusion||
does this always work?
Also, these two values represent the vertical component (the one parallel to the y-axis) and the horizontal component (the one parallel to the x axis) of the unit vector, the unit vector together with its components, form a right angle triangle where the hypotenuse’s length is always 1
ohh
i still dont get
how the factors work
😭
like the x/mgnitude
what does that even meannnnnnnnnnnnnnnnnnn
how does that even relate to the vector itself
$\hat{v}\cdot |v| = v$
BuilderDolphin
The original vector is <-1, 5> right?
yea
So
oh
this makes sense
but ike
5/sqrt26...
OH
WAIT
YOU GET
5
if you multiplty 5/sqrt26 by magnitude (sqrt 26)?
🙀
Yes
yk, i have no idea what clicked for you but nice
this kinda helped i guess
i did not understand the x/magnitude
and how that unit vector relates to the vector itself
Ok
but the equation literally shows it 🙏
The vector is a multiple of the unit vector
oh
ty both
huh
Fire stuff
what did
i thought this was "i do not"
instead of did
but it whatever

btw i jusy started cartesian vectors, is the unit itself gonna be hard? cuz i knwo wwe're gonna do dot product rule and do you guys have any tips for actually understanding the concepts cuz i think it's like pretty different than regular math
well it's a new way of seeing things i guess
🙇
Well, unit vectors aren’t be hard, and as a tip, i find right angle triangles as a good way to visualize things
Especially when you’re computing an angle using the dot or cross product, you literally can see the angle and connect the dots more easily
thanks
so break it up into x and ys?
thanks even tho no idea what that is just yet
splitting into components is always good when it comes to adding/subtracting
Yeah if you find yourself struggling to understand, it helps break things up
you'll learn it along with dot product
Any time
Like literally, i wanna procrastinate more, so pay a visit whenever you feel like it
Will do, ty
what do you plan to do after
Im not even math major
Mech
do you do proofs?
But calculus is a bitch everywhere
Rarely
Well i like em actually but yeah, they get over my head sometimes
you must be super good at math...
Half way through the degree that’s all imma say
Well if i failed calculus 2 times in a row, i better be
omfg 😭
Btw ya got any more questions?💀
If not .close and let’s switch to a general channel
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so this is my question
its part A
just finished it
and wanted to ask if i did everything correctly
sup brodie
😭
@native shard worry bout these mfs
ggs
wild
how old are you bro
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[Ticket #350](#〖senior-console〗 message): Prebanned kqllin2k.
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can someone help with this question, im kinda lost on the process to go through with this question
like ik u can peform the ratio test to etst for convergence with alternating series but, after that??
and why does this even matter
@red forge Has your question been resolved?
@red forge Has your question been resolved?
you have a sign error, but other than that, it's right up to the last limit. your conclusion after that is incorrect though
you have to use the given range of t from the problem
better conclusion i wrote here
what do you mean by sign error?
like just wrong + or -
the - after the equals sign is wrong
i thought since the -1^n+2
-1^n+1
i.e when n = 5
-1^7 and -1^6
so -1/1
so -1
hence move outside?
and would this be a correct approach :)
you ignored the absolute value sign
so i assume this would be allg, except not done
because we know this convereges absolutely for values of t > 0, but the only option left is when t = 0
so you can sub in t = 0 and then test for convergenece in other ways, (alternaating series probably) and hence you have yor interval of converegence?
is there anything here that is to do with the radius of converegnce, becuase ik its something related here but i have no idea how, not that it matters i dont htink if i can just find the interval?
then do it
oh yes you do have to
also yea im just asking like in regards to this question, what is the radius of convergence, comapred to the interval, i undersand the interval is literally the interval of values of t where T(t) is convergent to a value hence well defined, but in this case what does radius mean
im aware it doesnt ask for it
or is it impossible to excplain in this regards
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Hey I just finished AP Calc AB and I'm currently studying Calc 2. Thing is the BC curriculum covers parametric equations and polar coordinates before sequences and series, meanwhile my college does the opposite. Which one is better to learn first? Is there even a correlation between the two?
theyre relatively unrelated, so it should not matter which you do first
they're pretty interchangeable, yeah
I would recommend starting with parametric functions because they are a better continuation of what you did in AP Calculus AB.
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how do i prove for p(x)=(x-1)*f(x) that if x=1 is a root of p`(x) then f(x) is product of at least 2 (x-1)?
set g(x)=(x-1)^d h(x) where h has no powers of (x-1)
then differentiate with product rule
also does p have to be a polynomial? or can the powers of x-lambda_i be rational/irrational
well then generally it wouldnt be differentiable at eg x=1
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Hi, I'm a bit stuck on these graphs regarding in my statistics course. I'm not sure how to interpret them. What about these graphed power functions shows that one type of error is greater than the other?
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Can someone guide me to simplification which happens in the very last step? Where root x by 2 goes into power of e?
Please don't occupy multiple help channels.
Indice law,
x^(n/m) = mth root of x^n
isn’t root of root x smthn like x^(1/4), and the other thing being e^(1/2)
Yeahhh
$\sqrt{e^{\sqrt{x}}} = (e^{\sqrt{x}})^{\frac12}$
SELVATOR

Look at the first line.
Ohhhhhh
The guide has made a typo, so yeah
No worries
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i'm on Part D here
this is what i've done so far
i'm just wondering which quadrant my sum vector would fall in?
its a positive x and y so does that mean its quadrant 1?
<@&286206848099549185>
Yes exactly
okay thank you sm
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this solution has an error yeah, you need to multiply the error term by the 1/2
question is just find the firrst order Taylor series of arctan(x) around x=1, including the error term
yup
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status : 1
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
;/

How did y9u begin
and n=1
Yesbthats the way
and got f(2) in terms of f(1)
Do the same for all n lying in between 1 and 1000
then i tried to get f(2) in terms of f(999)
huh i didnt get that
try to get all those n in terms of f(1)?
No no no
Write the equations for all n in between them
Write them one below the other
To get a clear picture
Good
add everything?
Yes
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Can someone help me understand this result? How do they go from Cij = TijklmnEklaEmnb)VaVb to the second expression? Is TijklmnEklaEmnb isotropic because it is the multiploe if isotropic tensors?
I am asking about part (d)
@cursive vector Has your question been resolved?
@cursive vector Has your question been resolved?
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I understand how to get the second deribvative...
how do i find the bounds for when t is suppose to be c.up?
t-1=0
so t cant be 1
and t cant be 0
but what determines the < or > signs?
like uhh
idk how t explain
let me rephrase
t<0 i understand, but why t>1? shouldnt it just be t cant equal 1
idk what im saying
we are interested in where is the second derivative positive. there are two things which can switch signs:
t - 1 and 4t^3
so you have to account for the sign changes of both of them
ok
but it would still be positive for all values greater than 1 right
yes, that's what they conclude
if t < 0 then both t - 1 and 4t^3 are negative, so it cancels out and the whole thing is positive
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✅
Yes
Specifically here when dx/dt=0 for when dy/dt is not 0
dx/dt = 0
dy/dt =/= 0
Take caution when using this, as you might forget about holes within the function.
this sounds hard to do
Instead, consider finding where dy/dt = 0 and dx/dt =/= 0.
how do i find when dx/dt = 0 but dy/dt cant be 0
dont u just set dx/dt to 0
thats it
It really isn't
Just do when dx/dt=0, if dy/dt=0 at the same time t we end up with 0/0
Once you find those t values, you must plug them into dy/dt to test dy/dt =/= 0.
Which is a big uh oh
(Undefined and lots of bullshit occurs with 0/0, so we prefer dy/dt to not be 0)
Just to clear up on this real quick, Im doing problem 23, i have dy/dx = -3sin(3theta) / -sin(theta)
would i set the top to 0
individually
and bottom
Yes
There's some intersecting solutions, so be careful
The whole point of the secondary condition is to just not run into 0/0
oh i see
Hence
Also, to prove [this statement](#help-43 message), observe what happens at theta = 0.
Is this, stewart ?
yes
for the top
i have pi/3 and 2pi/3
for the bottom its pi, 2pi
what about intersecting stuffdo i need to look for?
because i dont see it
Are you restricting $\theta \in [0, 2\pi]$?
@stone jackal
yes
Just see when the solutions intersect (if both theta values produce 0 in numerator and denominator)
$$\left. \dv{y}{x} \right|_{\theta = 0} = \frac{-3\sin(0)}{-\sin(0)} = \frac00$$
@stone jackal
ah i see
it doesnt produce a 0 here
so
Oh, I misinterpreted your question, sorry.
my horizontal tangents would be = pi/3 and 2pi/3, and pi and 2pi?
How did you get 2pi/3?
Also, what do pi and 2pi represent?
@slim lodge Has your question been resolved?
sorry
pi and 2pi coem fromt he denominator
sin(0) = pi,2pi
-3sin(3theta) =
pi/3 and 2pi/3
comes from numerator
Oh, I understand now.
4 points?
Your vertical tangents are wrong. Your horizontal tangents are correct.
Sorry for the long delay; It took me a while to understand what you were saying.
Oh, are you trying to prove that denominator =/= 0?
i dont really know what im doing, all i know is that dy/dx = 0 for horizontal tangents
$$\dv{y}{x} = 0 \implies \theta = \frac{\pi}{3}, \frac{2\pi}3$$
@stone jackal
I agree with this part of your statement.
not with the pi and 2pi?
No, because those theta values cause both the numerator and denominator to be 0.
ah
sorry
No need to apologize; everyone is here to learn. 🙂
as for vertical tangent
can you walk me through per chance
$$\dv{y}{\theta} \neq 0, \dv{x}{\theta} = 0$$
@stone jackal
so set dx/dtheta to 0
set -sin(theta) to 0 then?
but
it does the weird thing
with pi and 2pi
so they cant be vertical tangents
right
so what would be the correct step to appracoh this?
,w -sin(t) = 0, 0 <= t <= 2pi
That's it. Since you never meet both condiions at any single theta value, you conclude that there are no vertical tangents.
,w plot (x, y) = (cos(t), cos(3t)), 0 <= t <= 2pi
i see
thank you
random question real quick is it possible to have the same points
for horizontal tangent
and vertical tangent
This is not possible, because the conditions directly conflict with each other.
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Let n be a positive integer. A board of size N = n^2 + 1 is divided into
unit squares with N rows and N columns. The N^2 squares are colored
with one of N colors in such a way that each color was used N times.
Show that, regardless of the coloring, there is a row or a column with at
least n + 1 different colors.
We're supposed to use the pigeon hole principle
hm ill have a look
is it possible to prove a stronger form where theres at least one column with n+1 different colours?
Wdym by stronger form
i didnt say row or column, i just said column
???
In the original question statement, they asked us to prove that there exists a row or column which has at least n+1 different colours. I'm wondering whether its possible to prove that there exists just a column which has at least n+1 different colours
I mean you can take cases
The question just asks for a general row or column
<@&286206848099549185>
@random mica Has your question been resolved?
@random mica Has your question been resolved?
Ok, assume that a colour was found in r rows and c columns. What can you tell about rc in terms of N?
1 min ill come to this
rc<N^2
That’s correct but not what we are looking for
Look for rc first not r+c
but
if say the colour is on every diagonal square
then r=N,c=N and rc=N^2
so im not finding any better bound
do i find a lower bound, an equation??
@slim osprey
You find an upper bound for rc
but the best upper bound is N^2
as i explained
at least only in terms of N
Ohhh, I’m so sorry you want to find a lower bound. I’m so sorry
Yeah, ofc the upper bound is going to be N^2
Yes! What does this tell us about r+c?
perhaps r+c>2n
Alright, this is true, so now what does this tells us about at least how many distinct lines each colour uses?
lines as in rows/columns?
Yeah
each colour appears in at least 2n rows+columns
Yes. So adding everything up, what is the least number of distinct (colour, line) pairs
N colours * 2n lines gives a lower bound of 2Nn distinct pairs
Yes, exactly. Now use pigeonhole principle given that there are 2N lines on the board (aka the rows and columns)
2Nn distinct (colour,line) pairs (pigeons), 2N lines (pigeon holes), means theres a line which has n distinct colours
Ok we have a problem, I see what went wrong. But the ideas we have our very close
Instead of 2n did you try 2sqrt(N)
This is what we need, and I’ll show you why
You prove it using AM-GM inequality
N colours * 2sqrt(n^2+1) gives a lower bound of 2Nsqrt(n^2+1) distinct pairs
now we need an integer approximate for 2Nsqrt(n^2+1)
and it has to be something like 2Nn+1
We don’t need to. By pigeonhole, we can say that one of the 2N rows must have at least sqrt(n^2+1) different colours. Then we can take the ceiling of this which is just n+1
oh
ok this was a pretty cool proof!
i guess the central idea was the distinct (colour,line) pigeons and the line holes
Thanks, sorry if I was confusing
then we started finding inequalities
Yes
no you werent at all
Exactly
Okay that’s good to hear
ill keep this in mind for next time thanks so much!
Sure! No problem
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A sub group of $A \subseteq \mathbb{N}^+$ is called a natural line if for every $a,b,c \in \mathbb{N}^+$ such that $a<b<c$ if $a,c \in A$ then $b \in A$. A subgroup $A \in \mathbb{N}^+$ is called a natural line with k holes if A isn't a natural line and there exists k different values $a_1,a_2,...,a_k \in \mathbb{N}^+$ such that $A \cup {a_1,a_2,...,a_k}$ is a natural line. \
Prove/disprove: there exists $m \in \mathbb{N}$ such that every sub group of $\mathbb{N}^+$ is a natural line with at most m holes.
prograce
I feel like this is wrong because for every m that fits for all the subgroups we can always make a bigger subgroup that needs a bigger m than it
I assume instead of the word subgroup you mean subset?
can we?
I think so yeah
Yes? if I assume a certain "m" is the utmost number of holes for every subset, then I can simply add to the biggest number "x" the number "x+2" to the biggest subset so now the number of holes is m+1
A subset can be infinite too by definition?
of course
if you want to try to prove the statement is true, then idk, maybe
||if the statement is true||
Is it not true ?
well I certainly don't think that it's true
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Given a 7x7 grid, each unit square containing a non-zero real number. Prove that there exists such grids so that the product of numbers in any 3x3 square is equal to the product of numbers in any 4x4 square and that the sum of every numbers in the grid is 2025.
Sorry my phone died earlier
I have solved the problem but i think you guys would come up with more clever solutions
By the way, i'd like to present my answer but don't know how. How would i create a grid?
You can try the tabular environment in latex
idk if something like this would work:
Fill almost everything with 1s, somewhere in the corner place 2 reciprocals, which'd make the total sum 2025
There'd be a total of 47 ones
,calc 2025-47
Result:
1978
those are the 2 reals you'd place in the corner
stupid solution, perhaps not what they wanted, but works
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 0.0005 1977.9995
oh and btw in the proof you wouldnt have to compute all that
it would probably suffice to refer to vieta's formula and perhaps present the quadratic
but then this 3 x 3 square
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 1 1
1 1 1 1 1 0.0005 1977.9995
doesn't have the same product
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Hey, I don't understand what I did wrong
same thing vro 
But my answer is 180° from the correct one
Then can't help U
Ok
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yo
you would need position of B=position of A
find some position function for B and A
the position function has to include time
so that we can do simultaneous equations
you dont need to.
have you learnt motion in a single dimension
and with constant acceleration
yeah
try modelling car B's position then at time t
S = 30t
B overtakes A when the total distance covered by B is greater than the total distance covered by A up until that point, try recalling the 3 Newtons laws of motion
that is true for Car A
good
now car B
notice car B has an acceleration
?
$s = ut + \frac{1}{2} a t^2$
have you used this formula before
mia
S = 20t + 2t^2
i just used the wrong formula
i thought all the formulas give the same results
now find t when S_B = S_A
5
yes
but why specifically that formula
s = 1/2(U+V)t
thats a formula?
i didnt learn that yet
s = 1/2(u + (20 + 4t))t
u havent learnt newtons laws of motion yet ur solving motion in 1D? im sorry what?
okay and u is?
nicee
if you have done integration, you can see the intuition behind these formulas
yeah
my course covers it next year
idk why
they are derived from velocity time graphs right
they can be
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4b)
have you found A already?
if you were able to do 4a, the rest should be easy. You just integrate it directly
,rcw
he didn't. should get the correct answer when you add the bounds
keep in mind ln(a) - ln(b) = ln(a/b)
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How would one find the partial solution to the ODE
I mean I know it's by undetermined coefficients but what do we guess exactly
1)write the power series for y^(4) and y''' by using taylors theorem for y and differentiating
2)expand the right side using taylors theorem
3)compare coefficients
So using the method of power series?
yes. why dont you try it?
I don't think that's what the professor wants, we learned that way further into the semester and this ODE problem is from like the start of the semester
Is there any other way to do it?
yeah, sure. substitute y''' = u
then you get u' + u = 1-x^2e^{-x}
do you know how to solve equations like these?
keep in mind i dont know what you learn by the start of the semester, so i might suggest methods that are not the simplest
Thanks man, wow haven't thought of that approach
im guessing your prof wants you to consider this as a homogeneous equation?
But it's not a homogeneous
you solve the homogeneous then find the particular solution
oh... partial solution.. didnt read that 😄
Yes that's what I was doing at first
But I couldn't find the general form of the partial solution
To determine it's coefficients
?
nothing!
anyways, once you solve for u, you just need to integrate a few times to get y, im sure you know that
wait i might be restarted
but cant u js.
substitute v(x) = y'''(x)
Already done.
^
lemme try
Yeah...
myb myb
Yea it's getting kinda out of control
What to do in this situation.. just patiently integrate?
<@&286206848099549185>
@uneven viper Has your question been resolved?
@hexed magnet @eternal pulsar @versed sigil sorry to bother guys, but did you find anything?
wait lemme try
oh am i stupid
is it js trivial
Wdym
solved for v already
oh u guys got here alr
whats left to the problem after this?
now u js integrate thrice
yeah, i dont see whats the problem!
the origianl poster seems to be dissatisfied that integrating this function is taking a while
Alright
Just patient integration I guess lmao
Thank you all for your help
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just change it to + C you are allowed
- 2C is the same as + C
ye or just replace + 2C to + C once ur done
C is arbitrary
its cuz C is some constant, so 2C is also just a constant so u can just call it C for constant
if that makes a sense
its a bit tricky to explain ngl
👍
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$$r = 3 + 2 \cos(\theta)$$
$$y = 3\sin(\theta) + \sin(2\theta) \implies \dv{y}{\theta} = 3\cos(\theta) + 2 \cos(2\theta)$$
$$x = 3 \cos(\theta) + 2 \cos^2(\theta) \implies \dv{x}{\theta} = -3\sin(\theta) - 4 \cos(\theta) \sin(\theta)$$
$$\dv{y}{x} = \frac{3\cos(\theta) + 2\cos(2\theta)}{-3 \sin(\theta) -4 \cos(\theta) \sin(\theta)}$$
@stone jackal
Can someone check my work?
looks right to me
Previously, I had been using an ugly formula, but I want to make sure I'm using this new method correctly.
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whats the difference?
or, when do i use double integration over single var integration?
well, both the integrals you wrote on the right evaluate to the same thing
so... there is no difference for this particular expression
what about this?
since $\int_{h(x)}^{g(x)}dy=g(x)-h(x)$
00100000
oh jesus. my memory is all foggy from my multivariable calc class, so I'm going to refrain from answering further, sorry :^(
o its ok
oh i got it
within double int is z=f(x,y) so im not really just finding areas
finding areas using double int is integrating 1 twice
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how do I do this on calculator I'm not getting correct one on desmos
it depends on the value of k
so just plug in t = 2
yes
that’s what we’re solving for
$3ke^{2k} = 4$
knief
also why did you do g’/f’
y’(t) and x’(t) were already given
no need to differentiate
oh yea mb 😭
yea using dy/dx = dy/dt / dx/dt
mhm
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why is c not 17
at october 25% is 17
keyword: greater
so is 50-17?
?
how do we do it
you said its 17 because its the first quartile
yh
but the questions ask for 25% greater than
if you used the first quartile here, it would be 75%
50% is your median
is it mot like this
oh
i see
well thats the label on q1 q2 and q3 yeah
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if i am finding the angle between two planes in R3 i used the dot product formula and got cos(theta) = some negative value
for example cos(theta) = -7/9 or whatever
do i take the positive of this?
like cos(theta)=7/9
or do i use negative
waterbeam
sam do u know]
Yes you can take positive of it
Taking positive of it will give the acute angle between planes while talking negative will give obtuse
But we usually care about the acute angle so yea it's ok
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My answer is ABC all looks correct
@deft tangle
From the above
We can get A U B = A intersection B
And when is that possible
If there is an element that is not in A ∩ B but in A, then A U B cannot be A ∩ B.
Also, A >= A ∩ B.
So A = A ∩ B.
Similarly, A ∩ B = B.
So A = B.
There is no vibe then intersection things mean B=C
And first one means A=B
@warped oar @floral fjord
ok
so $A \cap B = A \cap C$ \textbf{by itself} already implies $B=C$? is that what you claim?
Ann
what
(it's wrong)



