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np
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Given an M/M/1 queue with arrival rate lambda and service rate mu. If a customer arrives at a random time and the queue is empty, and we don't know if the server is busy, how do we calculate the probability that the server is busy?
seems like a poisson process
and they want you to use an Erlang distribution or something 
Suppose arrival rate is 1 and service rate is 3 for system stability how would I calculate the probability the server is busy when the queue is empty?
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was wondering on how to do this type of question for polynomial functions?
You can do some equations for a general polynomial of order 5 and slove recursivly
identify the zeros,
respective factors from factor theorem, then their power based on the shape of the curve around that zero
introduce scaling factor, determine that from the given g(0) = -2
1 -1 and -3
so my original equation is p(x) = (x+1) (x-1)^2 (x-3)^2
cause those tare the zeroes but idk
Looks good now input the g(0) = ... and you get the scaling factor
actually i thing it should be $p(x)= a \cdot (x-1) (x+1)^2(x+3)^2$
Tobi
you're not applying factor theorem correctly
if $k$ is a zero, $(x\red{-}k)$ is a factor
ℝαμΩℕωⅤ
its outright wrong
oh crap
because you didn't aply factor theorem properly
do you know what factor theorem states?
not really
i made an extremely brief summary above
yeh, now move onto the next zero
yes
so x+1^2
you'd want a scaling factor
what's that?
oh i see
what you currently have is a specific polynomial with those zeroes that doesn't necessarily satisfy the other condition
you're given g(0) = -2
don't know why they used different names here
probably a mistake with
the reviewer
you replace x with 0 and p(x) with -2
in the same step
no
you replaced things the other way
you replaced x with -2 and p(x) with 0
which isn't what you're supposed to do
yes
oh yeah my bad since p(x) is 0
i get it
i got 2/9 as the a
so p(x) = 2/9 (x-1) (x+1)^2 (x+3)^2
yes
thats our complete equation?
yeh
thanks a lot!
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How do I find the integrating factor for a differential equation of the form M dx + N dy =0 to make it exact ?
Are M and N constants or functions?
Oh
@blissful bane Has your question been resolved?
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hi! i am studying vectorial subspaces and i dont understand why P3(x) is contained in P(x). isnt P3(x) greater than P(x)?
by contained you mean it being a subspace?
polynomials
yes
sure
that's not very specific though
that doesn't tell me what the difference between P(x) and P3(x) is
ok ok
well p2(x) has all polynomials of degree less than or equal to 2
p3(x) has all polynomials of degree less than or equal to 3
etc...
yeah yeah
otherwise they're not vector spaces at all
and P(x) contains all polynomials
whatever their degree
hmm
so why would P2(x) not be contained in P(x) in that case
so, p(x) is like R for real numbers?
not sure what you're saying here
uhm
im still not sure what p(x)
like
its contains all polynomials, but like
its a universe of polynomials then??
I guess
but like P3(x) would also be a 'universe' of polynomials if I understood you correctly, there are also polynomials inside of it
yes
yeah like
the biggest one
i got it
idk how to verbalize my thoughts, but i got it
tysm
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Can you help me understand why this is wrong?
I was testing it and it says I’m wrong
@placid rose Has your question been resolved?
no
@placid rose Has your question been resolved?
Oh wait
Bro
I know I messed up but
It’s okay
I can close this
And nobody will remember
It will fade away into obscurity
And be gone 10000 messages away
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right isosceles triangle there is a circle on it that circle toches 1 side and its center is at the hypotnus and the circle also toches the shatrp corner i need to find the radius
Please don't occupy multiple help channels.
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look at the cylinders part of my teacher's work
the formula for the cylinder is 2pi * r * h * delta x
i can kind of see why he didn't include delta x in the integral function
but in this case should we have included it or not?
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How do i approach this?
(The anser should be written as x + iy)
Im thinking de moivres
But its my first time using it
So im not sure what to do
yes
convert to either cis form or polar form
each bracket
Ok
That will take some time
Working on it
I want to rewrite the 25 as something smaller
But i have messed it up before
What is a good method for doing it?
But how would i write it out?
I have a small clue
Both functions are periodical
By 2Pi
But how do i know its not = cos(0)?
Do i think of the closedt number possible to 25 (24) and the diffirence will be the answer?
25Pi - 24Pi = 1Pi
So cos(Pi)?
How would you do it if it was cos(163Pi/6)?
you subtract as many multiples of 2pi as possible
aka reduce mod 2pi
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Pleaseeee help with this question.
Its intergration by parts. ill send the question and then my work. I cannot understand for the life of me whats going wrong lol
let me send the photos from my phone
so i did the box where i chose
e^-x as my intergration.
and 3x-4 as my dx
so that should be
d = 3
intergration = -e^-x
so using intergration by parts it should be
= (3x-4)(e^-x) - INTERGRATION OF: (3)(-e^-x)
multiplying inside the intergration before to simplify
its then
= (3x-4)(e^-x) - INTERGRATION OF: (-3e^-x)
then intergrating it its
should be
(3x-4)(e^-x)-(3e^-x)+C
but thats wrong. im so confused lol
any help is appreciated! pls ping me ❤️ thanks
@glacial widget Has your question been resolved?
@glacial widget can you try multiple answers?
does it have to be simplified a certain way or is any correct answer acceptable?
any way
well okay for starters do you know the tabular method?
okay so you need to do integration by parts, you divide the the integral into two parts, the first part will be the bracket, and the second part will be the exponential function which is the (e^-x)
you select one to differentiate and one to integrate
ill show you on paper hold on
heres another example
i just dont understand wtf im doing wrong
like this is literlaly right
okay hold on let me try it
i just dont really undesrtand why youre suppsoed to multiply the stuff inside the intergration before intergrating
ok i solved the firstt one
i need the 2nd one now
thats hte one im really not understanindg
hey sorry im late
its ok!!
can you check the last answer and see if it will work, or does it need to be simplified
if it does, then I think I can explain it to you
alr tyt
uhh
the e^4x is supposed to be a common factor of the 3 fractions, is it written that way?
its not in the preview is it a bug
you have 3 fractions right
yes
they're all supposed to be * e^4x
but i have no idea how u got to that lol
bc the way im taught is this stupid square theory
OH OK NOW I CAN EXPLAIN
okokok do you learn better by visuals
lol
should I open paint
NO LOL
the way i was taught is thi weird
square thign
no no I mean like you want me to type it or open paint and explain on it
its fine lol
you differentiate the algebric term and intergrate the e
and then
its
a diagnol multiplication
and then - intergration of the multiplied bottom two
yeah but this complicates stuff
😭
I appreciate your help but I have to show my work in the stupid box way. ill just go to the Ta's or something unfortuantely
this method is similar to it
i just do not understand why i am getting it wrong
even using the box way
my work is right
so the integration of the multiplied bottom two yeilds another box right?
when you start out
you do the box thing
its the product of the diagonal
and a new integral
this
yes
did you do the new box
okay because the new box yeilds another box which is the last one in this case
but instead of boxes
you can write a table
it's better
let me show you
okay start by typing it like this
😭 i have no idea what im looking at
heres an example of one i just got right
column on the left (D) stands for differentiate, column on the right (I) stands for integrate
yay go you actually
LOL
okay did you write it
I dont understand waht that one is trityng to say though
like i dont get the + - thing
yeah thats part of it
when you write the table
you alternate between + and -
let me take you step by step hold on
you split the page
and put this
right
which is the box thing basically
yes
you add the + and -
start with the +
and alternate
you dont usually use them all, but add a bunch just to make sure
thats step two
got it?
okay now you have 2 parts of the integration
which should we differentiate and which should we integrate
alright
and intergrate e^4x
write it down and show me
on the first +
okay now when you have a function that can reduce to 0 by differentiation
you keep going till you reach the 0
you have x^2 - 7 right
yes
and then?
0
write that on the next lines?
that's your first stop
you stop when you reach 0
yeah you keep differentiating
you have 2x now
its gonna be 2
omg but intergrating is gonna take forever
then 0
whaaat
dnt u have to susbtituion rule
and stuff
hmm?
what substitution rule
to integrate that
uhh
okay what I do is
I put the e^4x
and then divide by the differentiation of the power
which is 4
☠️
😭
i think i may have to go to the TA because I think learning a whole other way of this is gonna harm me for my finals
like if my professor wants to see this stupid box method
i got all other 8 questions its just this one really messing me up
well yeah if it's gonna harm your finals to do it this way then yeah maybe not
but it's just so much easier
I understand :(. and i respect u sm for trying to help me but i gotta go to the TA to learn the way he wants us to learn it which is so.. ugh
tysm ! tho
oh no problem at all
u gave me the right answer which led me in teh right direction so
i appreicate it sm
I can link you a video in case you wanna learn the tabular method
Lol ill remember it before calc 2
alright
hopefully
have a good day/night!
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I need help with mathcad. I'm trying to plot a piecewise function and have the function peg out if it exceeds a max val or goes below a min. I have the piecewise itself working but I can't figure out why my other program isn't working
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Bump
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How do I tell if the coefficients of the sine or cosine term in a fourier series are zero or non zero?
can you give an example?
f(x) = 0 for 0 <= x <= 3, 1 for 3 <= x < 6 where f(x) = f(x+6)
By looking at the graph of periods of a function similar to this how would I be able to tell the above?
one thing to observe is that if you subtracted a constant 1/2 from this function, it would be an odd function
therefore all the cosine coefficients (excluding n=0) would be zero
so the fourier series would be of the form 1/2 + sum(n=1 to infinity) b_n sin(omega n) for an appropriate choice of omega
hmm i think i get it
what about a function that looks like 4 for 0 <= x < 3, or -4 for 3 <= x < 6 same f(x)=f(x+6)
same deal except the constant term would be 0 instead of 1/2
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how do i do this
i only know u sub rule rn
The binomial theorem is all you need here
id ibp this
whats ibp
oh
Be sigma and do
Pascal’s triangle
And distribute the x
😈
The do some power rules
That would go lit
In all seriousness I think setting u = x+8 gets you off and running
Wait
No I don’t think it does
i got to the integral of x(u)^8 dx and then
integral of x(u)^8 -8 du
idk how to get the X out
Yea
You don’t know
Integration by parts
Correct?
(u-8)(u)^8du
Hmm
I wonder what we can with that
Perhaps multiply out the u^8
And go from there :P
Continue with this
He got it
integral of x(u)^8 -8 du?
Oh you might be missing that
x = u - 8
You can't leave an x in there after your u-sub
Wait where's the -8 from
du-8=dx
or is that wrong
is du=dx
okay
cuz i used x=u-8 on accident
and it confused me
∫ (u - 8)u⁸ du
i see
Which is easier to get than the original, for sure
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how you solve this derivative
$e^{x^2}$
odokawa
Chain rule
Because you have a composition of two functions
there is a rule which say
ok
so it would be
$e^{x^2} . 2x$
@sage geode if not let me know
What's the derivative of x^2?
2x
Right, so it's $e^{x^2} \cdot 2x$
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✅
odokawa
and now we have to derivate it again
Product rule and chain rule
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,rotate
@pure nymph Has your question been resolved?
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What's the derivative of this function?
I think it's -5
But according to my book, it should be 5
give us some information on what the letters are
are P_K and P,_D independent variables from each other?
yeah
it's an economic function
and I need to take the first derivative of the function
okay when you say "find the derivative of the this function" you are being ambiguous since you have to specify with respect to what also
alr, sorry
it could be with respect to P_K or P_D
hmm
if it is with respect to P_D, you treat P_K as constant and the answer is indeed 5
okay yes it is with respect to P_D then
treat P_K as a constant and differentiate
I get it
so if it would be /aP_K
it would have been -10
yes
alright
thank you a lot
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I don't really understand where to start/how I can use double formula
just never see this layout of question before
Use the fact that sin(π-x) = sin(x).
Start from sin(2π/5) and apply the double angle formula.
wait what? do i spliy the 2pi/5 and go pi/5 + pi/5?
💀 OH WAIT
my bad
ik what u mean now
like pi/5 is theta
@shut lagoon
so im left with 2sin(pi/5) cos (pi/5)
whats next
Try the identity I gave you earlier.
This
@mellow olive Has your question been resolved?
bro idk ngl
idk how to use t he identity
😭
im just not seeing it
What is pi - pi/5?
is there also an identity like that for cosine?
where x is pi/5 right?
Yes that will give you the first identity
what i don't really get is why you couldnt just stay with 2 sin pi/5 cos pi/5
Because it asks to show that sin(2pi/5) = 2cos(pi/5)sin(4pi/5)
yes but if u didt know the idetity the u wouldnt rlly know what to do right
well at least in the textbook i didnt see that identity
oh wait i mean
not really in that unit
but yeah i get what u mean
thanks 😄
can i try part b and show u my work
b is just cos^2(3pi/7) - sin^2(3pi/7) tho i dont know what identity to use for cosine
@shut lagoon i thought that this was the identity so shouldn't the 4pi/7 be a negative and not a positive?
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$x + \frac{\pi}{6} = 3x,$
$x = \frac{\pi}{12}$
but what about the others solutions?
this functiosn have different phase how do i calculate all of their solutions then?
Yanek
Two things:
- What is the domain?
- What angle is equivalent to cos(x)?
Yanek
This is one set of solutions, think about quadrants.
Hi, can you please explain how to solve a problem like this? Step by step?
The call centre of a certain company receives an average of 30 calls per hour. The calls are independent of each other. 60% of the people who call the centre are men. The 100th person,
who calls the center gets a special reward from the company. Using CLV, calculate
the probability that
- there are at most 75 men among the 150 people calling the center,
- the waiting time for the caller(s) to receive the reward is at least 3 hours.
Sin, cos and tan have two quadrants with equivalent values.
Excatly, so you need the negative one.
$x + \frac{\pi}{6} = -3x$ but what about the phase?
Yanek
this gives 2 solutions?
so know this is just $\frac{pi}{12} + 2\pik , k \in Z$? and the other solution with 2pik?
Yanek
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What do you mean by phrase? This gives x = pi/12 + k*pi, and so does the other set of solutions.
so it doesn't matter that cos(3x) has phase of $\frac{2\pi k}{3}?$
Yanek
$$cos (x+\frac{\pi}{6}) = cos(3x)$$ $$=> x+\frac{pi}{6}=\pm 3x + k*2\pi$$
Good
i see
ok so when i have 2 functions f(x) = f(y) that have different phase i should take only the bigger one?
I'm not quite following here.
$cos(3(x + \frac{2\pi k}{3}))$
Yanek
@cunning breach would it work the same with lets say cos(2x) = cos(3x + pi/6)?
2x = -+3x + pi/6 + 2pik?
It dosen't matter which side you put the $\pm$, you will result the same.
Good
Try cos(2x) = cos(3x)
i was talking about the phase if it should be something different than 2pik there
i just not sure
but i quess you are right
2pi is the same as 360 degrees, which is a full circle.
cos(0) = cos(2pi) = cos(4pi). If this is what you was wondering.
yes, i know that, but the thing is the phase of cos(2x) is different than cos(x) and cos(3x)
You mind explaning what "phrase" is? I'm not native english, so I'm unfamiliar with some words.
im not native too so dont worry
wolfram alpha shows one solution that we didn't have
@cunning breach if you mind looking at that
Still don't get, if that's period, then it indeed would change, but you start with 2pi, since that a circle, else you need for a other persons explanation.
Speaking of wolframes three solutions, this might caused by + = +, + = -, - = +. You could try out.
Welcome.
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Hello, if the limite of a sequence function is +oo, does it imply that it’s inferior limit is +oo ?
If the lim exists then lim = liminf = limsup ;)
J’osais pas te redemander des questions alala je t’aime tellement
Ah d’accord donc + et -oo inclu
Merci beaucoup ❤️
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can someone explain what the max(S_x,S_y)/min(S_x,S_y) means????
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Hello, I really need your help I have been struggeling 2 hours on this. So I have a task that I need to complete for school. This is working with statistics of population and demographics.
So my problem:
I have found that the population in Malaysia is 32698,1 in 2022 (number 000') and that it is expected to reach 33379,5 in 2023.
In the population you have citizens and non-citizens. We have 30198,2 citizens and 2500,0 non-citizens in 2022. In 2023 it is expected to be 30415,3 citizens and 2964,2 non-citizens.
So that is a total increase of 2,083913132567% from 2022 -> 2023.
And for citizens an increase of 0,718917021544% from 2022 -> 2023.
And for non-citizens an increase of 18,568% from 2022 -> 2023.
So now if I calculate total population with a population growth of 2,08...%. Or I calculate the citizens and non-citizens with an population growth of 0.71% and 18,5% individually and add them up I get something completely different from the total.
How is this possible please help!
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can anyone help me with this
i dont get it at all
post the instructions
my ad
bad
i just did the top function = -2 but i dont understand why it works
oh hold on
nvm
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i dont get this question
Do you want to try writing out the IVT theorem first?
my bad it stands for intermediate value theorem
if f is a continious function on [a,b] and n is a number between f(a) and f(b), then there exists a number c such that f(c) = n
i graphed it on desmos it's not a continious function?
Right so the question here is telling you that f(0)<10 and f(4)>10, so if we blindly apply IVT, we should have that there exists x in (0,4) such that h(x)=10
yep
so the point of the question is to make sure you know that IVT is only true for continuous function
the function your working with here isn
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here we need to find f’(x)
and as i understand to do that, we need to confirm if it’s continuous then check for differentiation
i get how we proved its continuous
then we moved on to check for the differentiation of
- x≠0
- x=0
and again, we pretty much differentiated xsin(1/x) for the first term
are you sure lim xsin(1/x)=0?
but i dont get what we did for the second term
by the squeezing theorem, yea
the second term, as in the differential for 0?
oh oops, confused myself
undefined
you can't differentiate it because of that
the top one is product rule, the dne is because it is undefined
DNE = Does Not Exist
ah, okay
why did we use the limit as x approaches 0
and why did we put in it the evaluation of the first term
the 'because' part where they do the limit has a limit because we are dividing by 0
we can't divide by 0, and there will be a hole there
BUT if it approaches on both sides, it exists and we can pretend there is no hole
the -1/x(cos1/x) makes it necessary to do the limit there
well okay but then again
yea why
i mean why did we put it inside
ah, inside where, inside the cosine and sine?
sorry, I am confused as to what you are asking
the terms are within the limit
so we he doesn’t have to consider x=0
but anyway what is the definition of f’(0) @thin thistle
like in the most general sense, given some f(x)
limx -> 0 f(x) - f(0)/x - 0
is that the same as your expression here?
are u asking me because ur confused or are u asking me to get me to arrive to a conclusion
because im getting more and more confused
the latter
or more directly im saying that the f’(0) here is not the same as the definition of f’(0)
to clear the confusion, my question is,
when we want to check for the differentiation in x=0, why are we using the limit? and why are we asking about the limit of that very specific term
because definition of f’(0) involves the limit
but at the same time note that the limit your taking is not f’(0).
lim… xsin(1/x)/x
Because the definition of f’(0) is about the limit of f(x)-f(0)/x-0 as x approaches 0
As x approaches 0, x=/=0
so f(x) is still just xsin(1/x)
lusgnol you're confusing me too and I am in cal 3 🥵
😭😭😭
Your disagreeing with me on the definition of f’(0)?
no, I am disagreeing with you on whether it is relevant to their question
they are just trying to find domain of something and confused as to why the limit is needed, I think
it is relevant because the f’(0) they have written is completely wrong
the first term refers to the derivative when x≠0
well when x≠0, x is just a constant
and the derivative of any constant is 0
so we’re asking for the limit of that derivative?
to check for 0
which clearly doesnt exist in that manner
i am explaining this from a physics-applied-math viewpoint and not a pure-math-knowledge viewpoint BUT
this is piecewise because that hole gets in our way
yea
so we fill in the hole with the value it approaches using a piecewise function
HOWEVER the value that we use to fill it in was (likely, I haven't checked) acquired by taking the limit of f(x) approaching 0 when x!=0
the f'(x) ALSO is the same function, but there still is a hole there. we can use that function to find the value of the hole and fill it in
and why exactly are you filling in the hole?
The question is asking for the derivative of the piecewise function
well we want to know if there is anything there, so we take the derivative and the limit of that derivative as we approach the hole
we can plug 0 in here, to find the value of the hole
but we know that won't work because of the -1/x, we would be dividing by zero
which brings me to my second question
BUT even if there is no hole, taking the limit will get us the value at that point
in that limit
sin1/x is dne
as x approaches 0
i get it
but why is -1/xcos1/x = 0
using the squeeze theorem
-1<= cos1/x <=1
1/x <= -1/xcos1/x <= -1/x
shouldnt the limit for 1/x and -1/x be dne
good point 
the limit of cos(x) is DNE because it doesn't approach anything
the limit of -1/x is negative infinity because the divisor is so small it makes the number on top huge
ok the limit of 1/x approaches infinity so cos(1/x) should be DNE to my humble knowledge
the fact that it is multiplied by -1/x shouldn't matter, DNE * infinity should be DNE

lemme graph this
i think ill just take it as a rule that the derivative of 0 is dne and call it a day
my head hurts 😭
well yeah the derivative of x = any constant is DNE because of the slope
you can remember it because of the slope
my calculus 1 education at my school is actually garbage
but
what I was taught is that they don't have a slope
so you can just say it's 0
but maybe I should not be peddling that around 
sorry if its y=0 then its a horizontal line
so it is no slope
but if its x = 0
then it is a vertical line
which makes more sense when you do 3D calculus
so its 0 because the constant will always be y = 0 for you
i am sorry for confusing you 😭
it has been a while since cal 1
honestly not sure why its approaching 0 and not DNE but maybe squeeze theorem will help
you're welcome 👍
im sorry lusgnol you are very good at math but my simple physicist brain can only math that makes physical sense to me
Because it DNE and his doing something very wrong in his original expression which is why i keep talking about his expression for f’(0)
im talking about the cos expression
and i dont want to argue with you but your definition of filling holes to find the derivative is just not how derivatives are defined
not what i said
you fill holes to find the piecewise function's values at each point where the function itself does not suffice
works well enough for me in applied math
Is his final expression correct?
That’s my question to you
his f’(0)
but this is again not how derivatives are defined
derivatives refer to the slope
you can fill in such that the piecewise function can be continuous
I am not talking about the derivative, just the hole
the derivative is the function in question there
but I meant that for any function where we have holes we want to check out
also his f'(0) should be undefined there i think
and his derivative is right
im talking about the expression itself
the lim_{xapproaches 0} -1/xcos(1/x)+sin(1/x)
is this f’(0)?
i thought it was
it is not
hey man it's good enough for my professors
u mean f(x) - f(0) / (x-0)?
yes
and so we have f’(0)=limit of sin(1/x) as x approaches 0
not whatever your expression is there
Likely for you calculus class, you can assume that limit of sin(1/x) as x approaches 0 is undefined
where did you get this?
since that cancels out to 0/0
oh right
i divided by f(x) instead of x
but yeah i get what ur trying to say
but the limit in the picture is sent isnt talking about the definition
its using another logic
yes your f’(0) comes from nowhere..
it’s possible for function to be differentiable everywhere but the derivative to not be continuous
your trying to test for continuity of derivative at 0 but that’s simply not the same as finding f’(0)
that is if the derivative of any constant is 0, and if the derivative of any constant thats not 0 in that function -1/x * cos(1/x) + sin(1/x)
then the derivative of 0 would be the limit of -1…
you should not be caring about the derivative of constants
because the f’(0) is about the behaviour of the function as it approaches 0
u can’t differentiate a point if its not continuous
i’m talking about the continuity of the derivative
not the continuity of the original function
yes this is correct for the original function
the final expression you have in your original working is about the continuity of the derivative right?
well i understand my professor’s way but jts a pain in the ass, ur definition made it click easier
now i can use the same way of thinking for all similar scenarios
the final expression is not about the continuity
i would be very shocked if this is your professor’s way.
its about the differentiation of x=0
yes and i’m trying to tell you that your final expression is not the derivative of 0.