#help-13
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No problem!
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what does f[] (x) = mean ? (its meant to be like f ^box (x) )
can you show a screenshot/picture of the question
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Hello, I am stuck on a problem involving points on a 3D sphere.
For a school project I need to gather information on how gps works, and I nee dhelp on proving why we need a minimum of atleast 21 satellites. For gps to work there need to be atleast 4 satellites able to reach you, so there should always be 4 satellites above your head. I have found a way to find the minimum amount of satelites needed on a 2D circle, here is how
p1 is your position
a is the distance between the satellites
n*s is the minimum required satellites
r1 is the radius of the earth
r2 is the radius of the satellites to the center of the erath
note that on a 2D circle you need atleast 3 satelliets above your head
do you know whats the area covered by each satellite?
@gilded gate Has your question been resolved?
i do not
tho i could fgure out a way
i think
well you first can figure out whats the area covered by each satellite
he meant that a satellite can reach you if there’s no earth between you and the satellite
wdym no earth
if the satellite can draw a line between you and itself without going through the earth first, it can reach you, otherwise it can not
yeah and the circumference the satellite can be on is O wich i have shown how to calculate
this question has not been asnwered yet^
@gilded gate Has your question been resolved?
umm this reminds me of some concept involving location and i cant remember what it is 
i saw it in a coding question
got it!
True-range multilateration (also termed range-range multilateration and spherical multilateration) is a method to determine the location of a movable vehicle or stationary point in space using multiple ranges (distances) between the vehicle/point and multiple spatially-separated known locations (often termed "stations"). Energy waves may be inv...
not sure if this is the correct reference needed tho
i saw 'gps' and 'three satellites' so looks like it
@gilded gate Has your question been resolved?
@gilded gate Has your question been resolved?
if 4 satellites were needed would the answer have been 8?
@gilded gate Has your question been resolved?
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u again?
This problem is currently being discussed
Are you asking someone else's question?
yeah
huh
Why?
They got it lmao
i saw the question on a different server
i was curious to its solution
oh
.
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yo
second line howd they get lnx + 1+..
<@&286206848099549185>
the question
part b
It's just the induction hypothesis
d^k / dx^k x^k = k!
If you don't know it it's a trivial induction
Then the other one is just (k+1) d^k / dx^k (x^k ln x) which is given by the induction hypothesis
You mean the intuition?
yea
idk it's just a derivative
hm is there of explaining the logic behind it though
If I tried to give meaning to each term here's what I'd say:
Since d^n/dx^n x^n = n!, it makes sense to see it here along with a small correcting factor to account for the ln x
Since ln x is somewhat constant compared to x^n, it makes sense it can kind of just be considered as a constant, and therefore give n! ln x.
Then Hn appears to correct that approximation because ln x isn't really constant, and neither are its higher derivatives, which, interestingly enough, are (-1)^n (n-1)! when evaluated at 1
whats Hn?
The nth harmonic number 1 + 1/2 + ... + 1/n
ah
Which is close to ln n + 0.577 when n gets big
thx man
@grizzled stone Has your question been resolved?
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Does anyone know how to determine the value of this potency series?
is the question asking for the value or asking whether it converges
@crimson sedge Has your question been resolved?
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✅
answer denascite's question
if they aren't here to answer the bot's question then they arent here for that question either
Maybe they have the read channels hidden or something 🤔

Quite a few people end up making new channels cause of that
skill issue
@crimson sedge Has your question been resolved?
it is specifically asking for the value so we know it converges
but idk how to do that
does someone know how to find the value of it?
für alle = for all
?
no one willing to help
?
?
@crimson sedge Has your question been resolved?
Wild thought would be to express $cos(n \phi)$ in exponential form and use that...
chartbit
Ah fucc forgot whatever that symbol's called atm 
$\varphi$
IV
close 
LMAO of course it's almost that, those var's always get to me 
Honestly I hate the normal $\epsilon$ and always go for the $\varepsilon$
chartbit
$\varomega$
SilverSoldier
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
i hate $\omega$
SilverSoldier
Looks way too close to a normal w imo, arghhh 😷
$w$ vs $\omega$
SilverSoldier
yeah
Like if you're glance reading and not paying attention, and someone used both...
...actually, there's an idea 😈
View it as the real part of a certain complex number
Could you give me some more hints?
If you take what I said here, you should notice the sums split up into two things that should be easy to work with...
what famous formulas do you know involving trig functions and exponentials
nvm just z = r * exp(i * phi)
for z = a + bi
or what exactly do you mean otherwise)
?*
There is a very famous formula linking exp(i phi) to trig functions
It's named after a very famous mathematician
@crimson sedge Has your question been resolved?
Very famous in fact
He appears in almost all Math problems

Also
What does $e^{i\varphi}$ draw out?
VulcanOne
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what’s the answer
• Show your work, and if possible, explain where you are stuck.
@crimson sedge Has your question been resolved?
h is the height and is a function of time meaning at time t, h(t) tells you the height
so you can plug in any time for t and use the formula for h(t) to calculate the height at that time
for example, 1 second later
$h(1) = -16 (1)^2 + 69 (1) + 4$
riemann
,calc -16 (1)^2 + 69 (1) + 4
Result:
57
now you check all times in a-d and see which one gives the correct height in the problem
,calc -16 (1.35)^2 + 69 (1.35) + 4
Result:
67.99
,calc -16 (3.31)^2 + 69 (3.31) + 4
Result:
57.0924
,calc -16 (1.35)^2 + 69 (3.31) + 4
Result:
203.23
,calc -16 (2.96)^2 + 69 (2.96) + 4
Result:
68.0544
,calc -16 (3.31)^2 + 69 (3.31) + 4
Result:
57.0924
,calc -16 (0.69)^2 + 69 (0.69) + 4
Result:
43.9924
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could somebody check if my proof is correct?
,rotate
riemann
aaah true
wait what
you're trying to prove that if P(A) + P(B) + P(C) = 1 then A, B, C are mutually exclusive?
yeah
that sounds very wrong
my proof or the statement
the statement
what if you just have 3 random events which each are P(A) = P(B) = P(C) = 1/3
like uniform distribution on {1, 2, ..., 12}
and you choose like
A = {1, 2, 3, 4}, B = {2, 3, 4, 5}, C = {3, 4, 5, 6}
yeah the statement does sound sketchy
and the exercise did ask for me to show a counterexample if it was false
can you screenshot the original question
well there you go
this is important to tell us
by extension that also means your proof is wrong
because you hopefully shouldnt be able to prove an incorrect result
save that for proofs by contradiction
and when you're making the examples
dont just try to construct the ones that satisfy the statement
try to break it too and see if its possible
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<@&286206848099549185>
@plucky holly Has your question been resolved?
What have you tried?
i'm leaning towards the 4th option
Try thinking about how you calculate that again
How many options for 1st digit? How many for 2nd?
Can you list the even digits?
wait no
4 for the first
2,4,6,8
4 for the second
0,___
then 3 for the third
is that correct then?
the fourth option?
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Very quick question:
When integrating sin(4x+2) I can use u-substitution (I know its not necessary here, just taking a simple example) to get the correct result 1/4*-cos(4x+2)+C
But when integrating sin(4x^2+2) the result is something completely different. Why am I not allowed to use u-substitution here? When can u-substitution be used and when not? Only when the to-be substituted term is linear?
If you have
integral sin(4x^2+2) dx
and you do u = 4x^2 + 2
then du = 8x dx
The 8 is easy, you can create that from thin air, but there's not much you can do to produce that x
I can see how the x is a problem but what exactly do you mean with "produce"?
Well, that's what I mean, there's not really anything to do
are you simply saying that in the first example, we end up with dx=du * 1/4 which is a constant and thus can be taken out of the integral
whereas in the second example we end up with dx = du * 1/8x which is NOT a constant and thus cant be removed from the integral?
more or less
if the x was already there, then u-substitution is appropriate
∫ x sin(4x^2+2) dx
at first I thought that when my integral has du at the end I can put any terms with x in front of the integral just like if it were a constant, but I assume I cant do that because u refers to x, right?
right, if you have something like u = 8x, then u and x depend on each other
so x is not a constant in terms of u
x = 1/8 u, it depends on u
okay okay, that certainly makes sense
just trying to understand the method a bit more before blindly applying it
thanks for the explanation
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!15m
Please only use the <@&286206848099549185> ping once if your question has not been answered for 15 minutes. Please do not ping or DM individual users about your question.
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why does inverse sine in radians not give the original domain value of any sine input
it only works with degrees for some reason
Maybe because of the value of pi
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how do you compute the error vector from an orthogonalized matrix
my orthagonalized matrix is
[5 -10 5]
[0 1 2]
and my x is
[5]
[2]
original equations were 3x-6y=-1, 4x-8y=7, y=2
$$
\begin{bmatrix}
5 &-10 &5\
0 &1 &2
\end{bmatrix}
$$
DerpZ
ok so M^T = M^-1
yes
e=b-p
oh this is a linear estimator
can you quickly express this in matrix form
Kingvt
alright nice
the pain of latex 😭
oh is the error here an MSE?
ah so that what its called
@modest storm Has your question been resolved?
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Sorry for the badly worded question ahead but;
\bigskip
What exactly is the "projection" that the dot product describes? The formula of the dot product is given by $||\vec{A}|| \cdot ||\vec{B}|| \cdot \cos(\theta)$ for some two vectors $\vec{A}$ and $\vec{B}$ and the angle between them $\theta$
\bigskip
Now, from what I know, that formula describes the projection of $\vec{A}$ into $\vec{B}$ as a scalar. "How much of A is in the direction of B", if you will. But also $\vec{A} \cdot \cos(\theta)$ is another way to describe the same statement above, so why do we have to multiply by the magnitude of $\vec{B}$?
♡LexQa♡
The argument I heard is that this helps with the dot product being commutative, as $||\vec{A}|| \cdot ||\vec{B}|| \cdot \cos(\theta) = ||\vec{B}|| \cdot ||\vec{A}|| \cdot \cos(\theta)$ and that scaling that projection with $||\vec{B}||$ does not matter all in all since the the "projection" We are talking about is "relative"
♡LexQa♡
But that doesn't make much sense in my mind, since I know there is some sort of more abstract explanation to the dot product than that
||A|| for the A*cos one oops
Why the formula for dot products matches their geometric intuition.
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Dot products are a nice geometric tool for understanding projection. But now that we know about lin...
have you seen this
Noobs be like:Shadow
dot product is an inner product, so idk
im not a math knower
but inner product provides a notion of angle between vectors
which i think in turn gives you an idea of one going in the direction or not in the direction of another
by some amount
thats really the component thats giving you projection
@crimson sedge Has your question been resolved?
Yes but so does |A|cos(theta)
Does it not
But anyways I will give that video a watch
i mean the important part is that the dot product is giving you a notion of angle is what i mean
not that it is defined in terms of theta or not
there are inner product spaces without any geometric notion of angle at all
where you can still do projections
idk im just trying to intuit what your question might be
so i might be misanswering
it seemed like you were asking why the dot product specifically provides a sense of "projection"
My question is more of why is that projection given as something that is unique?
ah
Because it is not unique right?
it is
How so
Let H be a Hilbert space and M a closed subspace of H. Corresponding to any vector x in H, there is a unique vector m_0 in M such that |x-m_0|<=|x-m| for all m in M. Furthermore, a necessary and sufficient condition that m_0 in M be the unique minimizing vector is that x-m_0 be orthogonal to M (Luenberger 1997, p. 51). This theorem can be vie...
Isn't ||A||cos(theta) another description of that projection for example?
theres a lot of analysis in this proof
youre just talking about the dot product for one, thats not the projection
Hm I see so there is something more rigourous about it
i think
yea but there doesnt have to be
i mean im more just uhh
im linking you something that says clearly that it's unique
Projection of vector a on vector b is dot product of a and unit vector b, so for dot product to give projection of a on b, wouldn't magnitude of b have to be 1?
its probably not the most immediate way to understand it
Yes but take a step back from the formula of "projection" and just think of what the dot product describes by itself
Like I can just say it is that by what you said but that doesn't intuitively explain anything to me, I'm just regurgitating the same formulas in that case
dot product just describes how much of a vector lies in the direction of another
or how much of one is shared with another
thats the most helpful way to think about it imo
if you think about like uhh
orthogonality, or like primary colors, that sort of thing
it makes sense that a brighter color is going to have more 'red' in it than a darker color
so it makes sense to scale by the combination of colors
idk im just trying to think of ways to explain it 
Hmm I see I think it is just one of those questions where I have to explore by myself to fully understand it ig
I will look over this conversation and read over the links shared
but
understanding inner product is high level IMHO
like, you should be comfortable just thinking of it as saying something meaningful about how much two vectors point similarly
at least for now
Alright I already understand that part, but I guess I will suck it up until I slowly climb down that abstractness ladder lol
Thanks!
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Yeah it is very not satisfying
i mean
But I guess understanding has its limitations
abstractness removes all immediacy of interpretation lol
because you have to understand something completely agnostic of normal intuitive approaches
it just takes time

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you will see it in more contexts
inner products never stop coming up
I think I have yet to acclimate to the concept of abstractness, since at some point you just have to admit to yourself that it is impossible to explain something that is very abstract intuitively anymore
no i mean it is
there are people that understand stuff that you cant have a picture for or talk about IDK how but
intuitive is relative
True
depends on how you have constructed the math language in your head
Yeah
explaining, understanding, and like
demonstrating proving
Damn
all different stuff
Sometimes breaking down the whole structure and building it up again is the way to go
i feel like if you understand something you should be able to explain it
Lexqa send me ur screen time imma see how long ya use discord daily fr
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gl
I'm kinda curious as well lemme see
About 6 hours yesterday 
But thank you jan
Appreciate it
so the problem is something like why does c somehow lie "more" in the direction of a than b
?
Hmm not really it
but is this not a problem u have
✅
Yeah
I will say it is something I can't answer to well
@violet flume Has your question been resolved?
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Hey guys!
Ive been trying to freshen up on my math, and more currently linnear functions.
And i understand the first 3 questions. However i run in to the same problem everytime a question is stated like this!
if its f(-4), then i understand you place that instead of the x.
But when it says (f) = 30, i dont quite understand what that 30 represents. Or where to put it, or how to deal with it when we have a given equation already?
I understand that if we have no given equation it would basically be that (f) = 30 means its 30 on the Y coordinates. But in this case, im completely lost and i cant seem to find an answer when i try to google it :S
f(x) = 30
am i dumb too or does this look right
represets the function equalling that value for a corresponding value of x
so 30 = f(x)
30 = 3(4x-2)
solve for x
You mean on the top the red dot?
Yes because i initially didnt know the answer. So i pressed reveal answer and therfor it gave me a red dot
😛
ah, makes sense
@stone crystal what i've wrote out should be sufficent to understand
ahaaa
No i understand! You solve it as an equation
And remove the F
Thats what confused me as the other one you just replace X and not the entire f 😮
Ive been sitting for hours trying to see if i can understand this shit but couldnt see where the 30 went xD
Really appreciate your help a lot bro ❤️
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can someone help me with this
have you made progress so far?
A hint: ||try to transform the 4 in 2^2, 8 in 2^3 and simplify the numerator by denominator in the expoent||
Ig ya can rewrite that as
$2^1/4.2^1/8.2^1/16..
Yee
like this
Yep, and now just aply the sum of expoent
But to do this u will need the ||infinite geometric series||
okk
a1/(1-r), a1 is the first term
s=a/1-r
Yep
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can someone help me with this
Where ur stuck at
calculate A and B separately
i lose my that channel
how
what did you try
He can just do A/B directly coz things will cancel
how, A and B are sums
my idea was to separate each sum into odd and even tersm
the series of odd terms + the series of even terms
:/
lol
i am not that fool
I really thought he was serious
anyway try this
for A and B
ok
^
K
since we cant deal properly with (-1)^n
its better to separate into sum of odd and even terms
how can we separate
n ranges from 1 to infinity
so it ranges through all odd numbers and all even numbers
1 ,3, 5 .... and 2,4,6 ...
rewrite A for odd numbers
a change of variable, n= 2p (for even) and n=2p+1 for odd
Is this mains
yes
K
if i put odd numbers in n
$A = \sum_{p=1}^{\infty} \frac{1}{(3 + (-1)^{2p})^{2p}} + \sum_{p=1}^{\infty} \frac{1}{(3 + (-1)^{2p+1})^{2p+1}}$
i will get alternate - sign
Herels
nope
what is this?
what we are asking you to do
he probably doesn't get what 2p means
or how it got there
like I said, you do a change of variable for n=2p (which means for even term) and the other sum n=2p+1 (for odd terms)
$A = \sum_{p=1}^{\infty} \frac{1}{16^p} + \sum_{p=1}^{\infty} \frac{1}{4^p \times 2}$
Herels
good looking geometric series
yep
srry i dont get it
he has to be careful with p starting from 1 though
did you read our explanation ?
yes
and what didnt you understand
why you converted that series into this
again, I said that we cant deal with (-1)^n properly so we need to separate the sum into a sum where n is even and a sum where n is odd
ok
by a change of variable :
the first sum with n even : n=2p
the second sum with n odd : n =2p+1
and yadayada, easy algebra
now I got this
thats something we can now calculate
since its two geometric series
I wont do it, Im lazy
you do the same method for B, and you do A/B, youll have your result
im not a girl dude
help me plss
Im on a travel rn
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I know
QP cross QR gives 2(a cross b), however QR cross QP gives 2(b cross a)
The direction of the area vector just gets reversed
Yea
🗿
lol
@manic acorn Has your question been resolved?
Well, this is just a convention we follow, the area vector is taken vertically upwards from the surface we are measuring the area of. Your question is logically correct but it is what it is.
So take (QR x QP) as your answer.
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Can someone explain what the y=y equation is used for?
Im doing revision and i know that my question requires simultaneous equations to find x and y of a equation, but when would i use y=y?
when you have y = 3x + 4 and y = -x - 1
y = y will mean equate the 2 equations
so 3x + 4 = -x - 1
2nd example, if you have 2y = 6x + 8 and 3y = 6x + 9
then y = y means to turn them into y = 3x + 4 and y = 2x + 3 then equate them
so 3x + 4 = 2x + 3
(all the numbers are nice and divisble because i chose them so, didn't want any fractions in my explanation)
👍
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How do you memorize the square root values?
it just sticks to you the more you do trig problems? 
Is there an easy way for you to remember them all? I see they alternate 1-2-3 on numerator, or 3-2-1 on numerator and 2 on denominator, but wondering if there is a special tactic to remember them all
Hyp(2), shortleg(1), longleg(sqrt(3)) for the 30, 60, 90 triangle
thanks for the wallpaper
what?
And hyp(sqrt(2)), shortleg(1), longleg(1) for the 45, 45, 90 triangle
That's all you need to memorize
True
Ah OK I haven’t learned this yet but how exactly would you solve for 46 degrees? You need to draw a right angle triangle and calculate?
Yeah
Interesting, after finding calculations via the unit circle (1 unit) it can be blown up in size or shrink down in size it doesn’t matter the angle is going to be exactly the same
Pretty fascinating how far back thus unit circle was invented, BCE
And I’m still having trouble memorizing the fraction values for it lol
Lol
When a 30-60 triangle is involved, keep in mind that it has a root 3 and a half
Like 30° is like 60° in the unit circle
But they are flipped
@marsh pond Has your question been resolved?
Just memorize the first quadrant, and the rest are reflections over the axes. Like quad 2 is a reflection over y axis so the x coords flip signs
Quad 4 is a reflection over x axis, so y coords flip signs
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can i get help with c)?
could you tell me how you arrived at this formula please
It means the volume of a circle multiplied by the height.
so the integral is used to calculate the area
A cylinder is infinitely many, infinitely thin circles, stacked on top of each other
and the 2π is from the circumference of a circle
Yeah
so 2π * r where r is?
Your r here is the function
Your h here is the entire positive real line (0,inf)
Wait my bad I wrote that down wrong
$\pi \int_0^\infty (\exp(-kx)\sin(x))^2 dx$
Mr. Gamer
That should be your integral
where do you get the exp(-kx) from?
This was given
The radius is the entire function y(x)
Yeah
This might explain
$\pi \int_0^\infty y^2 dx$
Mr. Gamer
what was this formula called now again
is it this one?
how do i "find the total volume of all the beads as a function of k>0"
@quartz salmon Has your question been resolved?
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HELP
how are you getting 11 for a
are you just asserting that a is 11 out of thin air?
means
the first image didn't load
i don't know how you got 11 (which is wrong) for the value of a
he wrote a-d + a + a+d = 33
in the first image
why is a wrong
i need help
Bro
if you're using
a-d + a + a+d = 33
the a in that is different from the a in the general term of the sequence
note that in
a-d + a + a+d = 33
the a represents the second term
while in
a_11 = a + 10d
that a represents the first term
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help
Use the knowledge you know about AP
how
What have you tried
Can you show your work
ok
hint: do not make any attempt to determine a_1 and d
Don't do the work for people or give out answers
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I have solution to the last one too
Alr
I thought they will understand better just looking at the solution since its only calculation here.
nice you can
Not exactly, it's more beneficial to see their work and see what they messed up on instead of doing it for them.
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.You pretty much gave them the opportunity to take the work and run instead of having them do it on their own
I understand, im sorry😭
with this one
Don't ping specific people
• Show your work, and if possible, explain where you are stuck.```
Did you try anything?
1. I don't know where to begin 2. I have begun but got stuck midway 3. I got an answer but I'm told it's wrong 4. I got an answer and would like my work checked 5. I have a question about someone else's worked solution 6. None of the above
yes lemme show
7. I hate math and don't wanna do it anymore
7.i love maths i wanna do it all life .❤️
i need help
ok bye
guys
its time to sleep
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✅
what
i was going to say something but then decided against it.
help me with this
well, i guess i'm being ordered around now.
whta is meant by against it?
ok
should i go
??
or you will tell
something
when you decide against something, it means you decide not to do it or not to choose it
anyway, you asked for help, so now i have reason to say that your handwriting is kind of bad.
go sleep u did a lot today
so you now know that $f(x) = \frac12(3^x + 3^{-x} + 2^{1+x} + 2^{1-x})$
Ann
do you know how to find the minimum value of this function?
ok, great. then why not do that?
arithmetic mean is >= geometric mean
its kinda tough to apply
i already check
but i dont know
how to solve it
why not apply it to 1/2 (3^x + 3^(-x)) and then separately to 1/2 (2^(1+x) + 2^(1-x))?
ok
if you find that these things reach their minimum values at the same x, you will find that their shared minimum point is also the minimum point of their sum.
good night.
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13 and 14
@limpid tree Has your question been resolved?
<@&286206848099549185>
is it $\int^0_{-1} f '(X) dX ?$
Mehdi_Moulati
i don't think so
$\int^0_{-1} f '(X) dX = [f(x)]^0_{-1}$
Mehdi_Moulati
isn't ?
We want it in 2nd and 4th quad
It cuts y axis at 0,1 and x axis at 1 , 0
If u can use those
,w graph x³
,w -x3 + 1 ,x from -3 to 3,y from -3 to 3
Answer is -1
yeah of course since from the graph f(0) = 1 and f(-1) = 2
so f(0) - f(-1) = -1
you need to find the two points where the two curve are intersect
Ok so
0 and 0
Wait
I can't have a 0
It's impossible
One of the curves have 4/x
I must end up with a number
you need to solve the equation:
4/x = 5-x
when x = 1 and x =4
1,4 and 4,1
so know we just calculate the integral between 1 and 4
Those are intersection points?
Yes, but we only care about the value of x
to integrate in that range