#help-27
1 messages · Page 22 of 1
Wait I learnt the opposite: if au+bv+cw = 0 for all a,b,c ≠ 0 then it's dependent, but if au+bv+cw = 0 and a,b,c = 0 then it's independent (trivial solution as unique solution)
if the vecteur is null then a,b,c can be different from zero
but still gives zero as an answer
u,v,w are linearly independent if
au+bv+cw=0
ONLY if a,b,c=0
which is equivalent to saying:
u,v,w are linearly independent if
au+bv+cw≠0 for all a,b,c such that not all a,b,c equal 0
Yes now we need to prove u+v, v+w and u+w are independent but I'm struggling to get from au+bv+cw=0 for all a,b,c = 0 to a(u+v)+b(v+w)+c(u+w)=0 for all a,b,c = 0
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hi its me again..
s', not f'
same thing
no, not the same thing. you don't have a function named f.
also there's the issue that your handwriting makes it kind of hard to tell apart y and 4.
sorry
oh and you differentiated $-4y^{2/5}$ incorrectly
Ann
it should be $-\frac{8}{5} y^{-3/5}$ and not $-\frac{4}{5} y^{-3/5}$ as you wrote
Ann
so that's at least one algebraic screwup spotted
youre right
that and also tbh i would not have gone about differentiating s this way in the first place, unless you're under explicit instructions from your teacher to Use The Product Rule Or Else, or something.
how else would i differentiate it
but also i dont know what i did wrong with product rule aside from that algebra
i would have first expanded $-4y^{2/5}(y^2 - 54)$ as $-4y^{12/5} + 216y^{2/5}$ and then i would apply the power rule
Ann
much less headache
well like... that alone is already enough to get a wrong answer, so.
but if i fixed my algebra its still off
have you actually redone the algebra yet
yes
ok, show me
maybe you screwed up again but somewhere else this time
also by doing this you will acknowledge that you actually deliberately want to cause yourself headache
If you have decided to bring the negative sign in together with the term 4y^(2/5), this here would have been a + sign instead
you were not done...
i understand that later i should expand. but i also wanna make sure i know how to do power rule
what am i not done with
you are not done with redoing your work w/ the product rule
you mean like the two negatives cancel out?
the second term just disappeared
you thanos-snapped it
leaving a lone minus sign with nothing to its right
why did you do that
No, i meant your product rule is wrong
i dont understand
i dont see what disappeared
and i dont see what was wrong with product rule
There would have been a - sign there if your you didnt choose u to be -4y^(2/5)
oh i just never wrote that in cause it already wasnt looking right
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could've at least said "i don't need any more help from y'all" if that's the case, rather than just closing the channel in our faces.
its not that i dont need help its just that im tired of the attitude
and that you could also have communicated.
instead, you are displaying "attitude" of your own.
imagine slamming shut a physical door in front of someone. they will make a big deal out of it.
"tired of the attitude" while people try to help you
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where do I go to get quick math help?
I'm in math in society and need help with sets
post the problem(s) you need help with
eh...it's not that simple
if something is asking me for the compliment and the set is A=(xIx is even and x>6)
I don't know how to write the compliment, A'
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Anyone can teach me how to do this?
@winged torrent Has your question been resolved?
You can use the equation ax + bx + cz = S to eliminate one of the variables in P = xyz
Then for example you have P(x,y), and you can use standard methods to find stationary points (ie max/min)
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@brittle raven
case 1 is [-1:3/2[
ye
ye ye
so whats the solution
[-1:3/2[ in case 1
]-infinity ; 1 [ in case 2
without ( )
finally
edit it
and with ] at -inf
good
now we need to reunite those solutions
form the 2 cases
le reunion
i guess
ye
so
union & reunion
?
we use it in intervals
of those solutions ?
]-infinity; 1 ] ∪ [ 1 ; 3/2 [
reunite those
yes
yaay
]-infinity ; 1[
?
3/2 > 1
whats that
[-1:3/2) ∪ (-infinity ; 1)
use )
it's so confusing to use [ and ]
3/2 > 1
no
do you know how to reunite?
it means to combine the solutions of both cases into a single interval
in first case we have x < 1 and in the second case we have -1<x<3/2
the combine of the solution is ]-infinity ; 1 ]
cuz 1 < 3/2
is that false ?
1 < 1.5
yes
and on the right side of the interval you write the biggest possible value it can have
here the biggest value is 3/2
not 1
so if we test 1.2
for example
it gonna works ?
yes
oh ok
so whats the final answer
[-1;3/2( ∪ )-infinity ; 1 )
)
i forget hh
yes
(2;3)
now we have to check
if our final answer
contains a restricted value
so we do the intersection
of our final answer
with the restricted values
(-infinity;3/2) intersected with (2,3)
(3,2) isnt an interval
in an interval the bigger number is on the right
and a number cant be smaller than an interval
it can only be smaller than a value from the interval
what that means ?
thats what we need to do
to see if our final answer and the restriced values have something in common
if they dont
then our final answer is correct
if they do
we have to change our final answer
they dont
why
we don't have any number from this set (2,3) in our intervale
yep
)-infinity;3/2(
]-infinity;3/2[
If you were a teacher, how many points would you give for this question?
idk
depends on how many questions there are in total
this is preety hard
so i guess more than the rest
3 pts HHHH
3 pts out of what?
20
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In the rectangle ABCD, |AB| = 60. The point M is the middle of the side [AD]. The point N is on [AD] with |AN| = 20, what is the length of [AD] if the triangle MNC is right in N
I don’t know where I should start lol
And I should make them equal right ?
With the Pythagorean theorem right ?
Never mind I don’t need help lol
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I’ve made a mistake somehow
Oh never mind I’m really dumb I can’t read a question
It’s |AD| that we want not |ND|
So it’s 110
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using the shoelace method
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Hi ,can someone help me with the Fourier transform of "Λ(t/T)signum(t)" ?
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hello! i’m stuck on part ii
how would i find the domain restrictions on this function?
i looked it up on desmos and it seems to be (0,120) but how would i get to this answer through an equation?
Do you know how to draw a quadratic graph?
i think so
but this one has a negative in front of the x^2 so would my parabola be flipped?
my graph on desmos says it’s right side up
Try putting it without p(x)
so like a y instead?
Yep
It's still upside down u shaped
it’s u shaped
It looks more like n than u?
Do you get it now?
i’m still confused on how would i find my domain?
So for what x values is the y value bigger than zero?
would i have to split it in half?
That part is the graph is positive y values
For what x values do we get those y values?
120? right
so i’d half to put parentheses on them?
The parentheses represent a range of values
wait i’m a little confused
(a,b) means a<x<b
if the second half of the parabola has a negative slope, i would have to ignore that part right?
No, because y is still positive
but if the slope is negative then wouldn’t i leave that out of the domain?
We are not looking at gradient
sorry i should have been more clearer
im still confused how would i find this through an equation
math is so harddhifhfi
I thought you were asking for what range of x is p(x) positive?
But you are asking for what x is p'(x) positive?
yeahh
Basically you had the right idea here
When is the slope positive?
Like for what x values?
so i would have to find the max point? and set my restriction based on that?
Is that a coordinate?
Is the gradient positive when x is less than zero
im not sure what gradient means
Sorry slope
Is the slope positive when x is less than zero?
i think
Yep so you need to include that part in your values too
okayyy
wait would that make sense with my equation?
what do the negatives represent?
Oh in your question you are only interested in x being positive because it represents sales of an item?
I see
Then this is correct
Using the equation, you can draw the graph yourself instead of using desmos
Then everything else is the same
is there any other way
like would i be able to find the derivative and do something with it?
Yep you can, so what is the derivative in this case?
Not quite
ohh
i have, but my teacher didn’t tell us to use it for these questions
so i would have to do it the long way right?
In that case drawing the graph is the easiest way
alright :))
if i were to find the derivative, how would it help solve the answer?
like how do i use it to solve the question?
So in this case the derivative is 120-2x
This is positive means 120-2x>0 so x<60
Did that make sense?
No problem
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Because the maximum gradients occurs at the point where the derivative of the gradient (aka the second derivative) is 0
Which is also the inflation point
so max gradient is always the 2nd derivative = 0
not always
pls explain
second derivative can be used to tell you locations of stationary points of the first derivative,
which could be local max/min or inflection
generally it doesn't give you the location of the absolute max gradient
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can anyone explain to me how this works?
is the denominator p?
https://opentextbc.ca/intermediatealgebraberg/chapter/10-5-solving-quadratic-equations-substitution/ if you never saw it before
then im using the reduced quadratic equation https://en.wikipedia.org/wiki/Quadratic_equation
In algebra, a quadratic equation (from Latin quadratus 'square') is any equation that can be rearranged in standard form as
where x represents an unknown, and a, b, and c represent known numbers, where a ≠ 0. (If a = 0 (and b ≠ 0) then the equation is linear, not quadratic, as there is no
a
x
...
last line is my prefered formula for quadratic equations 🙂
quick paint scribble sorry haha
yep i drawing a blank hahha
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@kindred mango Has your question been resolved?
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How do I simplify this?
what was the original question?
find the derivative of x/2-tanx
@turbid sphinx Has your question been resolved?
for starters, the - needs to become a + because of the -tanx turning into -1/cos²x
in here i mean
I thought the derivative of tan was sec^2?
oh
how would I find the derivative of -tan?
the derivative of -anything is the same as the derivative of anything except you add the minus
because you can write - as -1 x f(x)
and a if you have a function multiplied by a constant
the constant stays as it is when you derive constant * f(x)
ok i see
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its a practice test (non-graded)
@restive river Has your question been resolved?
<@&286206848099549185>
Use Rienman
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[\tan = \frac{1}{3\sqrt{7}} * \frac{\sqrt{7}}{\sqrt{7}}= \frac{\sqrt{7}}{21}]
dopediscorduser
Where's my mistake?
it would just be $3\sqrt{7}$
Azo
@short iron Has your question been resolved?
Oh
I must have mixed up my opposite and adjacent values
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Tc f = 5 + 12
A manufacturer shipped units of a certain product to
two locations. The equation above shows the total
shipping cost T, in dollars, for shipping c units to the
closer location and shipping f units to the farther
location. If the total shipping cost was $47,000 and
3000 units were shipped to the farther location, how
many units were shipped to the closer location?
need help someone
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@vivid wren Has your question been resolved?
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hey i have a question
im struggling with this issue
the question is in spanish which makes it worse
but i can translate it to english
for context this is it in englihs
it basically says
Perian Herring inserts announcements into her envelopes for extra income during her spare time. Her initial cost for obtaining the cost information was £200.00. Every envelope is £0.2 and she is paid £.04 per ready-made envelope. Consider that x represents the number of envelopes already prepared.
Perian does a job. She makes 50% value from what she spends to do the job (40p). She has already spent £200.
The question is to find out how many envelopes have already been prepared.
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not sure where to start
In plain English, that’s inverse prime equals one over prime inverse. U can see a pattern in English
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whoops lol
okay so for this your u is right
but also consider that $u = 10 - x \implies x = 10 - u$
MellowDramaLlama
make an extra substitution 🙂
yep! now just solve like you normally would with the power rule
np
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what does log e evaluate to?
is it one?
when you say log do you mean the natural log?
When you just say log base 10 is in implied
no, the base depends on context
Very true. But if you just write log(x) base 10 would be the most common. Hence why it would be implied
no, wolfram says otherwise, so do many. context is necessary
no, i mean what i said
,w log 10
uh i’m confused
got a feeling that my question of "When you say log, do you mean natural log?" went unanswered.
bruh
whether that was by carelessness or by deliberate decision, i do not know.
regardless the derivative is incorrect
so
Turns out it's an engineering thing
would it be 0?
depends of you're differentiating with respect to x or something related to x
with respect to x
how could i forget that i am not the kind of person who deserves answers to their questions.
ye x is 0 mb
where's the double log coming from...
can you show your work
ok so log means natural log
it wouldve been hella nice to know this by explicit confirmation and not by contextual inference alone ngl
im not sure if 1/log(e-x) should be d/dx (log(e-x)/log(e-x)
bad notation and sign screw up
???
note that you have actually differentiated in your first step,
writing f'(x) there is highly inappropriate / wrong
im supposed to be d/dx first right
you're supposed to have ln(f(x)) = there
we cant use ln lmao
why not
i'm just using ln here to unambiguously refer to natural log
if your using log for the natural log just write log whenever i use ln
log(f(x)) =
if you insist
alrigh
you also miswrote cos as cot in the numerator when copying down the question
im tired lmao
as for the part involving the derivative of log(log(e-x))
you're missing a - sign from the derivative or from distribution,
it is unclear which
how?
start by showing your work for the derivative of
log(log(e-x))
, with adequate application of chain rule
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maybe im just dumb …
Jake drops his piece of cake off his porch and half a second later it hits the ground. Find the instantaneous velocity of the cake when it hits the ground. how do u find the instantaneous velocity??? 🤠
Instantaneous velocity is the velocity recorded at a specific point of time
what would the equation be tho 🧍🏻♀️
v = gt?
I’m not an expert in that but all I can give is an example
since this was not taught in my school and I had to google it in order to find the answer
imagine yourself
and let’s say you have a bf or gf shouting for help from a far place
yes
so you run to them, and your velocity is not constant
so at some point, your velocity will be slow
and at some point, it will be fast
It’s like you’re running and getting tired so you’re slowing down
Once you get enough energy you start to get back to your original speed
mhm
Let’s say I want to know what’s the velocity at a specific point of time when I’m running
That’s called instantaneous velocity
let’s say at the 5th second of running, my velocity is 2ms^-1
OK
is my instantaneous velocity at 5th second is 2ms^-1
You can search up for more, this is what my memory told me
maybe searching is better since it’s been a while I’ve dealt with these questions
i think its dealing with free fall
so it would be like
(9.8m/s^2) (.5s)
RIGHT
RIGHT
i think im rigt
HHANK YOU
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anyone know how to do these
@fathom rivet Has your question been resolved?
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how do do this - 10 to the power 2 route -2
the first step would be to write it in a way that can actually be understood by someone other than you
i am in myp1
maybe write it on paper
i cant
why not?
writing it with the keyboard so far has produced 10 to the power 2 route -2, which i can't say i understand.
but yes, send a photo here.
let us not riddle ourselves.
it is OP's responsibility to make their question understandable.
okay, so 10^(2 sqrt(-2))
...have you had any encounters with complex numbers before?
yees
right...
OH THIS PERSON WASNT OP LOL
and have you also encountered complex exponentials?
niet
namely, are you familiar with the formula e^(ix) = cos(x) + i sin(x)?
no
hey this looks fun
well. yikes, i guess
we can use
ok @midnight dirge you can take over from here
$z^s = e^{s \log (z)}$
10^2i
errrr
that does'nt meke sense
i knoow
$10 ^ {2 \sqrt{-2}}$
exactly
exactly
$2 \sqrt{-2}$
this
$2 \sqrt{-1} = 2i$
my mind - ...
wot
$2 \sqrt{-1} = 2i$
$2 \sqrt{-2} = ?$
idk
Separate sqrt of -2
so
2i root 2
ok
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Hi
How many times would 0.86 go in 100
use division
How?
Here let's start with a simpler problem, how many times would, say, 2 go into 100?
50
1.5?
So basically 30/0.86?
multiply both by 100 to get rid of the decimal. You're not changing the result
Where did the 30 come from?
10000/86 and use long division formula
I’m figuring out how many coffee cups (0.86cm2) would go into a 30 metre room
How do I do that

Like we’re filling the whole classroom
Or 30 cubic meter
Sorryyy
all good
It's the same process as the simpler problem I gave before
When you wanted to know how many times 2 goes into 100, you divided 100 by 2
Yup
Just like that
Oh
You deleted it but I saw it
That equals 34.88
,w 30/0.86
pstttt he has to convert to same units
Yea I did coz I thought it was wrong
If it has to be the same unit then we can add another 0
Not sure how to convert the cups to cubic when I'm not sure what 0.86 cm^2 is even measuring
i think he means 0.86 cm^3 but idk man
That's what I assumed
even so 30/0.86 would not make much sense
How many coffee cups - 0.0086m would fit into a 30m room
30m?
Assuming both units are cm^3, you would be correct with your 34.something answer
do you mean 30m^2 or 30m^3
what kind of room is 30cm^3 lol
if you were given a poorly worded problem then it is not your responsibility to untangle the wording
I’ll start from the start
I need to figure out the volume of a coffee cup - I will paste the picture below
This coffee cup - I need to find out how many of these would fit into a 30m^3 room. Firstly, I need to find out the perimeter and the volume for this in order to find out how many would fit in the room
Can someone please help me finding out the volume of the coffee cup - like edges etc
I need to fill the whole room to the top
That’s the room below
I need to figure out how many of these cups would fit into that room
Can someone please help?
are those cups empty? like, are we stacking cups inside each other for this?
or are we treating them as solid, filled-in objects
Yes they’re empty
because then we need to know the thickness of the paper they're made of, to know how high a stack of n such cups will be
@devout lichen channel occupied please move
No basically they’re solids
Like they’re trash and we need to figure out how many would fit in the room
They are empty tho
so we can stack them inside each other
However it will fit in the room
Inside eachother, randomly stack, just throw them in etc
So how would I do that- firstly I would have to calculate the cup
well it does kind of matter. are we looking to maximize the number of cups filling the room?
I’m hearing
like, how thick is the lip of the cup? i.e. the ring at the top of it
i imagine it can't be more than a few millimeters
hm.
yes, you've sent that here already
i mean, we could just naïvely divide the volume of the room by the volume of one cup, and get an estimate on how many cups will fill the room if we just toss them in haphazardly.
but i believe we can do better.
ah wait hold on! the diagram DOES tell us the thickness of the lip, even though it's indirect
110 - (97+10) = 3mm
right, so then a stack of n cups would have height 110 + 3(n-1)
(the full height of the bottommost cup plus n-1 lip thicknesses)
and the cross section of the stack is of course a circle of radius 89mm
n is the number of cups in the stack
Ohhh
we don't know how big our stacks will be, as it will matter what orientation we place them in the room
the room is 4m by 3m by 2.5m, yes?
Correct
let's consider three orientations: heightwise, lengthwise and widthwise
Sure
in each case, we will find the number of cups in one stack, and then we will approximate the number of stacks using the area of the corresponding wall or floor of the room
Don’t we need to find out the volume of the cup first?
no actually, we don't
Oh
we are stacking cups inside each other anyway. their volumes overlap a lot.
circles of identical size packed optimally on the plane have a packing density of about 91% - this is the ratio of a circle's area to that of a regular hexagon circumscribed around it. you can calculate the exact value of that on your own time, but for now we can just roll with it.
It wants me to find out the volume tho
what this means is that, for example, when putting stacks in height-wise, we will have only 91% of the area of the floor be covered by the circles that are the cups viewed from the top
we can do that separately. it will not be necessary for our cup stacking calculations.
do you follow this?
Yes I do
right
ok
so the top-down area of a single cup (and also a stack of cups) is the area of a circle with radius 89mm
er
diameter 89mm, sorry
so in square millimeters that will be
,calc 89 * 89 * pi/4
...why is the bot not responding
whatever, i calculated that on my own calculator.
6221 mm^2 give or take
and the floor is 4000 mm * 3000 mm, before adjusting for packing density
so that gives us the number of stacks as (4000 * 3000 * 0.91)/6221 = 1755 (rounded down)
and to find the number of cups in a stack inserted height-wise, remember n cups give a height of 107+3n mm
thus, 2500mm ceiling height gives us (2500-107)/3 = 797 (rounded down) cups in a stack
our room is in metres tho - will we have to convert it at the end?
i have already converted all lengths into millimeters.
the results of my calculations are dimensionless anyway bc they are counts
anyway, 797 * 1755 = about 1.4 million cups in the room.
1,398,735 is the exact value from the calculator but we are not being infinitely precise anyway
well that's if we are putting them in vertical stacks
let's see what happens if we try to arrange the stacks horizontally instead.
there are two ways to do that: lengthwise or widthwise
no thank you, I just needed one way
just to make sure this is how many cups u can stack in verticle order?
yes
also i just checked
putting them in widthwise you can squeeze in about 2% more cups
whats the volume of each one tho?
,w conical frustum volume
oh... thank you so much
...okay, the bot is unresponsive again
Haahahhaha
and i am getting a volume that is like three times bigger than it's supposed to be...
oh wait no
i'm using diameters as radii again 
right ok so
480 ish ml from those dimensions
,calc 400 * 300 * 250/0.48
62500000
er wait no
480 not 0.48 my bad
i did it in cm this time
so only 62,500 cups that way
Result:
6.25e+7
the volume of one cup is 62,500cm?
