#help-43
1 messages · Page 65 of 1
That's the way to do it
No u sub at all?
What do u mean by u sub then
🤔
I can’t find the message unfortunately
But yea
Apparently you can
So I was interested in knowing how
no AI helped me so far except for introduce some overwhelming definition of that integral
What do u mean by u sub bro
x=tan u is a u sub
Do u want to do x=u and come back to where we started
So then there probably isn’t a u sub approach
!noai
Please do not trust ChatGPT or similar AI tools for mathematical tasks, as they often generate output which "sounds correct" but has numerous factual or logical errors. Use of these AI tools to answer other people's help questions is strictly against server rules (see #rules).
do you know your trig identities for integrals?
are you sure it wasn't a different integral?
something like 2x/sqrt(1+x^2)
@cerulean sinew Has your question been resolved?
Yes
I believe so
For this you could do tan^2(θ) = x^2
But then I just don’t know how to integrate the result you get
Like sec^3(θ) in this case
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Someone please help me
the slope of a tangent of a curve at a point is the derivative of the curve at that point, right?
so just differentiate the equation first
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Can someone help me with the following problem: Let X be a quotient space obtained from $B^2$ by identifying each point x of $S^1$ with its antipode $-x$. Show that X is homeomorphic to the projective plane $P^2$
Surf
Not really sure where I’d even get started. I have the definition of the projective plane but that’s all I can really think of
@native jetty Has your question been resolved?
What definition do you have for RP^2 and what do you know about it?
The projective plane $P^2$ is a quotient space obtained from $S^2$ by identifying each point x of $S^2$ with its antipodal point -x.
Surf
I know it’s compact and the quotient map $p: S^2 \rightarrow P^2$ is a covering map. My guess is I want to find a similar quotient map from $q: B^2 \rightarrow S^2$?
Surf
Well using that D^2 is homeomorphic to the upper hemisphere of S^2 may help
Some adapted homeomorphism should show equivalence between S^2 / antipodes and D^2 / antipodes
Hm. Can I split S^2 into two hemispheres and use the fact that the intersection is S^1?
Well you could take some equivalence class on S^2/~ (notice that since the antipodes are identified, you have all the "information" on the upper hemisphere) and show some natural way of mapping it to an equivalence class on D^2/~.
Ah. Each point has one representative in the upper hemisphere, so each element has one representative in it. If it is not, then it’s on the equator and then it is exactly S^1 so we get something like B^2/ x ~ -x on S^1
Yes
They are the same equivalence class aren’t they. So it is precisely how we defined P^2 in the first place
Now I just have to show that the quotient map restricted to the upper hemisphere is a homeomorphism right. It’s not enough to show the classes are the same.
Or is it?
You can just use something like projecting the upper hemisphere reprensentatives x down onto the disk continuously and the identification on D^2 works out inconsistencies that would've arisen normally because of how the equator is identified on S^2/~
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The question is to solve for x and y
But fir the second line, idk whether to multiply or not
this is correct so far
you should simplify the left hand side (think: what is -1 - 2) and then multiply both sides by x to put the variables on one side
also please note that x != 0 (you should write that somewhere to not forget)
so if, when solving, you get the solution x = 0, discard it
Ok
Could u explain why
which part
$(x - 1) - 2 = x - 3$, right
no after that you get $x - 3 = \frac{4}{x}$
then you should multiply by x on both sides
so that all your x's are on the left side
that's correct
Yes
solve it then :)
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
bro im not trying to be cool its easy
listen ibrahim
everyone in this server knows you can do it, we all know your capability and ability
but our other friend wants some understanding of the problem
so we're helping em
alr
@modern arch Has your question been resolved?
Ok

wdym?
the man is a lil confused but he wants to help
yes
did you end up solving this quadratic?
oh okay cook
Havent done y yet
Can I have tips for solving word problems
I’m rlly bad at them
should be a positive one
Oh
cuz -4x - x = -5x not -3x
Ic
the sum of terms you break should be equal to the original term
damn
Do u have any tips
I just want to finish sims and be done
Bit I also have to do trig functions
The naming of the equation is hard for me
I did plus
For?
after using +1
,rotate
Couldn't find an attached image in the last 10 messages.
Well this one is correct
Ty
But could u help me with the second one
I’m struggling with that
But I have to go do something soon
Let me see
Really really soon
sub the equation and check the determinant
Pls explain these terms
substitute one of the terms out so you have just 1 polynomial, idk if it's a quadratic or not, but then find the determinant to check for the roots, they might not be real (i didn't have time to solve it)
this is a resource you could check out https://en.wikipedia.org/wiki/Discriminant
In mathematics, the discriminant of a polynomial is a quantity that depends on the coefficients and allows deducing some properties of the roots without computing them. More precisely, it is a polynomial function of the coefficients of the original polynomial. The discriminant is widely used in polynomial factoring, number theory, and algebraic ...
After substituting and finding a value
How do I find the next pls
Not In a rude way
Idk which equation IM suppose to put the found value in
try both and see which is easier to slove
solve
ideally try to stay within the second power
example?
The second equations
Like those sentence math questions
I forgot what their called
in general try to set up equation to make it easier to work with, and list out the facts
Ok
solve for one and plug it back to the first, and then solve for the first, if the second is a quadratic then it's easy, just look it up online, other wise try factoring, the rational root theorem can help, and test to find at least one root if you can to build a start
Can u use an example
Like using equation a and b
That’s sort of thing
D>0, there are 2 real solutions
Wait is it
Oh yeah
you mean word problems?
@modern arch Has your question been resolved?
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✅ Original question: #help-43 message
Yes
word problems require familiarity with the terms used in the question, so what kind of word problems do you often face - financial (money-related), physical (physics-related), or some other domain?
financial and physical
I have some questions
sure, you can show some of them.
which one would you like to do first? but from the looks of the paper you have done them all anyway.
Number a
I didn’t rlly udneerwgamd, I was copying what my teacher was saying
right.
I didn’t want to disturb him bc everyone was following and I couldn’t understand
personal opinion: ask anyway!
I’m scared of judgement
Everyone seems smart and it takes me a while to understand math
that says more about them than about you, OP.
but anyway, so you are given a rectangular room of area 20 sq. meters (sq. = square).
if you let the length of the room be x and the width be y, can you write this out in an equation?
Er X x Y = 20
so xy = 20, that is absolutely correct.
your question then says that the length is increased by 3 metres and the width is increased by 1 metre.
dang columbina this is fire teaching
like actuallty
explains thru the stuff
Moving rm, I’m in class
even i understood parts when i read
Brb,
you know that x was the length. so if the length is increased by 3 meters, what is the new length of the room?
back
X+3
correct!
now, the width is also stated to have increased by 1 meter. what is the new width?
6+1
then correct! so the dimensions of the new room are (x+3) metres and (y+1) metres respectively, agreed?
Yes
good! you're now told that these two changes double the area of the room.
the old area, as you recall, was 20 sq. metres. what's the new area?
40
good! can you now set up the equation for the new room dimensions and area?
I was gonna send the solution
I noticed there r more
!nosols please.
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
Ofc u would 😭
Ah fair enough mb
@modern arch Has your question been resolved?
No
I don’t understand the second instruction
Oh so we find x and y right
you know that the new dimensions are (x+3) and (y+1), and the new area is 40.
can you set up another equation with these values?
Kind of
Doing so no
Know
I was having class and my teacher doesn’t like us with our iPads so I had to go off
then better finish your class first.
you can come back after your classes are done. besides, it's a little rude to be using devices in classes, in my humble opinion, on top of having your attention split between two places.
I recommend not involving the units at this stage.
Oh ok
also, don't use x as a multiplication symbol when the variable x is also present. it's very confusing.
Class is starting again
Bye and tysm
sure.
Next is the test
you don't have to be! your time first.
dang this chat is so nice, its giving me butterflies in my stomach
i think i didnt chew em properly 😞
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What does the phase plot in the Fourier spectrum mean?
@rapid crescent Has your question been resolved?
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Hey I’m doing this function question from a practice test and have no clue how/why it works/how they go the answer
First pic is the start of the question
Second is what it’s meant to become
given a function f(x), will you be able to find f(|x|)?
Yes but I don’t get how the -|x| will turn into that
so first, what do u do to find f(|x|)?
the method would be similar once u understand
You just flip the parts that are negative across the x axis
is this what u mean?
Yes
Ohhh
and flip it about the y axis
when it is f(|x|), u take the right half cause |x| is positive
and the right half is positive values of the function
so similarly, for f(-|x|) we take the left half (cause that represents negative values of x) and flip it about the y axis
hence the 2nd image here
no problem!
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How can i prove that lines BD and BE are parallel? All i know is that the distance between A and D is a third of the distance between A and C, and that the distance between A and B is half the distance between C and E. My teacher said that it’s possible to solve this by using vectors and algebra, but she also said that there is another way, sadly without specifying this ”other way”.
BD and BE arent parallel, i think what you mean is vector BD=k×(vector BE)
Yea sorry for wording it wrong thats what i meant
Yea but only that the point C is placed right inbetween Point A and B, but im not sure how that is supposed to help
It isnt place between A and B in the picture tho?
Yea its placed above A and B but the normal from C is between A and B if that makes sense
Ye i think i need the full question ngl
If you draw a line straight down from C it Will land right inbetween
So CA=CB?
Yea
And the size ratio between AD and AC relative to AB and CE is the same also if that makes sense
No sorry AD and CD relative to AB and CE
Since if you multiply AD with two you get the length of CD and if you multiply AB with two you Get CE
So it almost seems as if the triangles ABC and CDE are similar
But i dont know and of the angles so idk how i can prove it
Are you given EC=2AB as lengths or as vectors?
Lengths
Would it help if it were vectors?
She didnt explicitly say that, but maybe we were supposed to assume it?
If it were vectors we could actually prove it, without and there isnt enough info
Yea we got the question orally so im guessing she ment vectors but said the wrong thing
Since if we put A,B,C as unchanging point then E could still be anywhere on the circle (C,2AB) (as in C as the center and 2AB as the radius)
Yea im following
Welp ima assume vectors for now then
So do you want to prove it with vector addition or geometrically
Preferably geometrically
Also note that what we're doing is pretty proving E,D,B are collinear, meaning they are all on the same line
Yea got it
If vEC=2vAB, then EC is parallel to AB and EC=2AB (v is short for vector)
(And also that E and B are on opposite half planes defined with the line AD as the boundary)
If i draw a line from A to C now and i know EC and AB are parallel can i also know that the size of angle A and angle B are the same?
Angle C*
Yes
Isnt that technically enough to prove that triangles ABD and DCE are similar in form?
Since we know that the size ratio between AD and CD, and AB and CE are the same
Yea since all angles are the same dont the coherent sides need to be parallel to each other since the angles of the lines are the same?
Lines with the same rate of increase must be either colinear or parallel or something along those lines right?
Sure
Do you need help with the vector addition approach or can you do that on your own
Why tf did it autocorrect to an emoji
I know that one from before but thx for all the help
Np
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I need help with this. I am confused on how to solve it since there is no volume. A right triangular prism with a right isoceles triangular base is shown. The height of the prism is equal to 9 centimeters (cm), and the base of the right isoceles triangle is equal to 8 cm. What is the volume of the priwsm, rounded to the nearest cubic centimeter?
no picture to go with it?
I would send a picture but it is on my chromebook and i am using Discord on my computer
the volume of any cone or pyramid is 1/3 the prism it was cut from
i.e a prism of its base and height
I understand
can you confirm it looks like this
-# another situation to say thats what she said
Yes it's similar
if you calcuate the area of trianngle and multiply by height you will find the volume
I'm looking for the volume of it lol
Ah okay
mb volume
The volum it’s Triangle base area*heigh/3. You need to find the triangle area.
😉
How do you find the area of a triangle
Why did you wink 😭
B*h/2
Oh okay
So 8 multiplied by 9/2?
No, triangle height.
9 is height of the prism not the triangle
So nine multiplied by 8/2?
No, first of all you need all triangle mesures, then you need to apply pitagoras and find the triangle heigh and then you can do triangle height*8/2
Oh okay
So 8^2+9^2?
It's a right angle isosceles triangle and there's only one triangle like that
No, you need to find your hipotenuse. First.
the base is the hypotenuse
Right.
So 9^2+x^2= 8^2?
?
red is your base of prism
vro the base of the isosceles triangle is 8
Then apply pitagoras and find hipotenuse.
I thought the hypotenuse is 8^2
It’s not necessary apply triangle formula for area.
🙂
since the isoceles triangle is a right angled triangle both base and height = 8
Then B*h/2
I thought the height is 9
look at the left diagram of prism the height of prism is 9
So base divided by 2?
Base=8 and triangle height=8. 8*8/2
oh
35.2?
Yeah this is the triangle area.
Then you need apply de volume formula+Triangle area*height(figure height not triangle)/3
105.6?
how did you get 35.2?
I did 8.8*8/2
64/2=32
Apply the formula again with 32. You are doing great.
🙂
105.6?
(32*9)/3.
105?
32: triangle area, and 9: height./3
96
Excuse me it’s a prisme you don’t need divide. Only 32*height.
the height of triangle if you consider the hypotenuse to be 8
32 multiplied by 9?
@weak trench First we need the triangle alutra making pyramids deaphea we go back to Find the area Finally the volume.
How do we find the area?
can you confirm what they labelled 8 in the diagram
I thought it is the base
Yes
then the length of hypotenuse is 8
The you need to find the triangle height.
do you understand this ?
How is the hypotenuse 8 though?
.
the baseof the prism is a right isoceles triangle
OHH
Okay
What do I do next?
from here you can see the side opposite to right angle , hypotenuse is 8
please move to #chill for memes
Do you remember how to do Pythagoras @weak trench?
a^2+b^2=c^2?
Catet?
There should be a property for the height of an isosceles triangle
since the triangle isocelese , 8 is the base the other two sides are equal in length, the base angles are equal you can find the base angle
Leg.
Ah okay
the height of an isoceles triangle drawn to the base side bisects it
Do you remember how to do it?
Isn't it also equal to half its length
only for right isoceles triangles
x^2+9^2=8^2?
H^2=8^2-4^2. Because you have another triangle in.
do you understand this, you can find the hieght of triangle from here
Won't the other side be 45 degrees?
the other angle?
Yeah that one's right, you don't need any trig
x?
Actually you do, I lied
So both of the legs are 45?
not the legs, the angles
Oh okay
do you understand it
Why is it 45 though?
hm.. what is an isoceles triangle?
OH. 2 sides are equal
yes, two sides are equal, along with two sides the angles opposite to the equal sides are equal
So now what
you know one angle is right angle = 90 can you find other two angles?
45? 😅
you know because i said earlier xD
Yeahh
you can use fact that sum of all angles of a triangle = 180
so 90 +x+x -=80
you can find x
Oh because all triangles = 180
Yeah
now use this fact
What does bisect mean?
divide into two equal parts
Oh okay
So since it bisects it, it splits into two right triangles?
yes
BC was equal to 8cm AD divides BC intotwo parts BD = DC = 4cm
now you have to use trigonometry
Ohh because half of 8 is 4
AD is the triangle height.
what is tan x
Do i use Soh Cah Toa?
Yeah.
What is the opposite angle?
45 degree
is the adjacent angle 4?
not angle but side yes 4
4 it’s.
Oh okay
Do I multiply them?
Think about the angle that do you have wich leg crate the angle it’s the adyacent.
Ah I understand
muliply who
45 and 4
tables?
you have tan45 = opp/adj = AD/4 so AD = tan45 *4
Or in a calculator.
So is the answer 4 because I put it in the calculator?
yes 4 coz tan45 =1
Right.
Do I use the Pyhtagoren Theorem or the Triangle formula?
Pythagorean*
Area = base*height/2
Is it 8?
Wasn't it 4?
4 is the height
is the base 8?
base was 8
yes
So 16?
yes
is that the final answer?
finally multiply area by height of prism
Alr
Is it 64?
16*9?
I thought the height is 4?
oh that was the altitutde of triangle the question has given height of prism
9
Oh
144?
yh
Is that the final answer?
Okay, I'll keep that in mind
i need help with another question also
A cake pan is in the shape of a right rectangular prism 20 centimeters (cm) long by 20 cm wide by 5 cm high. The pan contains 1,000 cubic centimeters (cm^3) of batter. Approximately how far is the cake batter from the top of the pan? A) 1 cm B) 2.5 cm C) 5 cm or D) 7 cm
what have you tried
oh I got it right
ic 🎉

I need help with another question. I've tried it and I got it wrong
mm.. ok post it
Anya has two different sized cylindrical coffee mugs. The larger mug has an internal height of 15 centimeters (cm), and the smaller mug has an internal height of 10 cm. Both mugs havwe an internal diameter of 8 cm. Which of the following is closest to the difference in cubic centimeters (cm^3) between the internal volume of the larger mug and the internal volume of the smaller mug? A) 63 cm^3 B)251 cm^3 C) 754 cm^3 or D) 1,005 cm^3
I tried C but it is wrong
,w pi165
I did pi multiplied by 4^2 multiplied by 15 for the big mug. I also did pi multiplied by 4^2 multiplied by 10 for the small mug
ok their difference should be 251
approx
oh so I was right 😭
@weak trench Has your question been resolved?
I also need help again. I tried 64 but I got it wrong
hey do you need any futher help?
Hi, yes please
state your troubles
I have this word problem. A building contractor has a pickup truck with a rear storage area in the shape of a rectangular prisn. The storage area has a length of 80 inches (in), a width of 60 in, and a height of 44 in. She wants to fill the entire storage area with equal-sized rectangular prism-shaped bricks with lengths of 8 in, widths of 4 in, and heights of 2 in. How many bricks can the contractor fit in the storage area of her truck?
okay lets take a moment to see what given data we have
we know shape of the total available storage here is a rectangular prism
so we can find the volume with its given dimensions
Yeah
lets calculate that first
Is it 64?
we have length as 80 inches, width as 60 inches and height as 44,
so the formula for a rectangular prism is l x w x h
its important we use the correct units
volume is always cubed
just multiply 80 with 60 with 44 to get the total volume for rectangular prism
now, we have the dimensions of individual bricks, which is 8 inch, 4inch and 2inch as length width and height respectivelyt
so we can find the individual volumes of each brick
using the same formula,
Okay thank you
so this is the answer you were getting
64 inch^3 is the volume of each brick
the questions asks us how many bricks in total can fit in the storage area
so we divide the bigger volume by each individual brick
So 211,200 divided by 64?
yess!
3296.875?
your answer would be 3300
it divides it completly
you shouldnt get answer in decimal
your answer would be 3300 bricks
I put it in the calculator
that doesnt make sense
the calculator returns the perfect 3300 value
perhaps maybe you messed up the input
?
I also need help with another question
okay sure
Wilber wants to make the pond in his backyard bigger. It is currently a cone with a radius of 30 meters and a depth of 15 meters. He wants to increase the radius to 40 meters and the depth to 20 meters. How much more water will the pond hold, in thousands of cubic meters? (Round to the nearest thousand cubic meters.)
hey awesomeperson i'll just get back to you in a minute oke
Okay!
okay
im here
do you want the solution or an explaination too?
im suggesting the explaination will help you further
in understanding the concept
Explanation please
oke
so we know the shape of the pool is a cone
so
do you know the formula for volume of cone?
or volume of cylinder
Is the volume of a cone 1/3 multiplied by pi multiplied by r^2 multiplied by height
?
yeah
so
we can find the volume of the cones to see how much water they hold
now there's two methods of solving this,
either we can individually find the old volume and new volume
then to find how much MORE water it will hold, we (new volume) - (old volume)
to find the difference
so we can calculate both of these separately or we could take them into one equation and then solve them by substituting the values
which method would you like? or i could show both approaches
The second method please
In the first image, is that a r?
yes
thats the radius
since the new pool will be bigger, it has a different radius as specified in the question
so we cannot take r and r
we must take r and R
since the values are different
Is the second image's radius a 40?
yes
What's next?
Alr
still took more than one image smh
if value of pi isnt given, its easier to take 22/7
if its given, then use the specified value
have you understood it @weak trench
Is 19000 the answer?
Why did we subtract the second volume with the first volume?
yess, since the question asks us to round the answer to the nearest thousand, it will be 19000
the questions asks us ''HOW MUCH MORE WATER WILL THE POND HOLD"
now
this asks us the difference
how much more
that means
whats the difference between the amount of water it used to hold and the amount of water it holds now
since the new pond holds more water
The answer is wrong
we subtract new volume with old volume
what's the answer?
It doesn't say
does it have a specified value for pi?
Nope
19000 what we get after rounding to the nearest thousand
i made no mathematical mistake
Well idk why it says it's wrong
could you screenshot the original question?
The question is on my chromebook and I'm on computer for Discord
Input integer
Er
something may be wrong with either the software or the data may be different
pelase recheck!
Yeah it's right
ah well
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are you sure mate?
Nevermind then
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tt
who is arabic here?
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Show that if $1, z_{1}, z_{2}, z_{3}, \ldots z_{n}$ are the $(n+1)$-th roots of $1$, then
$$(z-z_{1})(z-z_{2})(z-z_{2}) \cdots(z-z_{n})=1+z+z^{2}+z^{3}+\cdots+z^{n}.$$
Halex
I know $z_k = e^{\frac{2k \pi i}{n+1}}$ but not sure how to proceed
Halex
here's a small hint: if two polynomials of degree k share k roots, then they are equal up to multiplying by a constant
@dawn marsh Has your question been resolved?
Yes, I know that $$1-z^{n+1} = (1-z)(1+z+z^2 + \cdots + z^n)$$ but I'm not sure I can use what you mentioned
Halex
i'm pretty sure you can use it because it is a very elementary thing, every time you factor a polynomial by finding its roots you are using it implicitly
but if you don't like it you can also use this: if both polynomials coincide at n+1 different values of z then they must be the same, since their difference is then a polynomial with n+1 different roots but degree at most n (hence the difference is actually zero)
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I keep just getting the start again
What are you trying to prove?
What are you stuck
I keep getting the same thing as the start
Sinx/1-cosx
Hmm okay let me see
Use identity for 1-cos^2 x
On line 4
You were almost there
Whats the trig identity which uses cos x and sin x?
Ohh sin^2x
isnt the denominator you should multiply1+cosx instead?
Whoops yea
Can I simplify this more
yes you can rewrite this fraction first
I’m not sure how
it should be sin^2x /sinx(1+cosx)
It’s not that type of question
I’m running on like two hours of sleep lol
and a Dunkin refresher
look at question 34, what did it ask
nahhh that is crazy
See I got sleep paralysis
for like the first or second time
So now I’m worried to go to bed
fried 😭
anyways you finished the question
Yup I’ll be back tho since I have a quiz on Wednesday so today and tommorow I redo all the homework from this unit
Because I love torturing myself
dawg.
listen it works I have an A
and I’m used to this I got like fifteen disorders and disability’s ( diagnosed ) so I got to work through it somehow 😀
you don’t want to know the way I study for reading chapter quizzes
damn thats sad, just ask for help if you need help
instead of redoing the work here, why not find new problems to tackle?
I do have help it’s just the way I do work I guess
I mean I forget the problems by the time I redo them
and It’s easier to ask my teacher questions on certain problems instead of coming with a whole truck load of problems she has not seen
alright, I won't ask any more. sorry for intruding.
no worries
@haughty smelt Has your question been resolved?
if you finished please type .close, thanks!
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Linear algebra...opposite of finding unit vector...but i don't get it
?
yes
(1/||v||)* vector
pyth. thm?
what if the vector is 3 d
i dont get it
ok..
what about this question
does vro know the distance formula
@lofty mountain are you aware of the formula to calculate the length of a vector
yes
what is it?
Pythagoras theorem
h^2 = p^2 + b^2
... yes
if i have a vector [a, b] what is the length of this vector, then?
using pythagoras
ren
good
do you understand what we have to do here?
no,m
okay. you've been given a vector
they say this vector has length 1
but you have to compute the length and confirm that yes, it actually does have length 1
since you know the distance formula, can you compute the length of the vector for me?
ok
idk the distance formula
i forgot
you literally just
???
oh..that is distance formula
the distance/length formulas are the same thing
once more
h = sq root. of p^2 +b^2
okay
for the last time
i know that you know the distance formula. it is the same thing as the length formula
ok
your question asks you to compute the length of the vector given and confirm that the length is 1.
since you clearly know the formula, please compute the length of the vector
5
?
sq root (3)^2 + (-4)^2
there's a 1/5 outside
what is 1 / 5
it is outside..but don't know from where it came
what do you mean "from where it came"
if u is a unit vector, then it should follow this formula i.e.
(1/ II v II)* v vector
... yes
continue from there please
(1/ II v II)* v vector = 1
no-
ren
yep
sorry for the issue
no no
it's okay
it's not your fault
sometimes i have trouble understanding what people mean as well, don't worry about it
i'm here to help, so it's my job, don't worry
if you're done, you can close the channel with .close
ok thanks
np
.close
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I am trying to understand the equations for an inverse kinematics linkage system I found in a documentation. I am already have the solutions however I can't get my head around why these work. I provide the pdf where the full equations are in.
Understanding of first calculation b1: Calculating b1 when X is positive is just 90 - Arctan(X/Y). I understand this like i drew it in the picture. I don't understand the part why you add L3 to X when X is negative. Wouldn't b1 just be adding alpha to 90 when X is negative because the angle is larger than 90 then.
For the equations of c1 and c2 I cannot visually understand what is being done there.
For the other equations I haven't even got there because I struggle to understand even these.
@maiden spear Has your question been resolved?
@maiden spear Has your question been resolved?
<@&286206848099549185> I don't know if such a questions is fitting for the channel or if it is to big. Please let me know then I can search for somehwere else 🙂 Thanks
Probably most of the members in usa timezone so they might reach in to help soon
This is beyond my knowledge so just be patient for few hours😂
Ping @ helpers may help
Ahh okay good to know 😄 Thank you, then I'll just wait a bit!
No worries!
@maiden spear Has your question been resolved?
so hmm
c1 and c2 are the elbow angles and we got tan(90 + b1) which is just -cot(b1)
Ytan(90+b1) is the horizontal reach of the upper arm through b1
subtract l3 for the pivot offset from centerline
divide bby -y, then the arctan is the angle from the pivot to elbow
c1=90-b1 - the angle
what's left is the interior angle at the joint and c2 is the same thing
Thank you for your help!
So I am confused are the angles in the graphic not actually what is being calculated? So is the actual c1 like what I drew in the picture the red angle? And the other parts are highlighted in blue and green are these what you meant?
yup
D1&D2 use c1&c2 via sine rule to get the actual distances from bottom pivot to each elbow and then a1/a2 are just law of cosines from there
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So I tried 20 a with u sub. I had $u = 2x$ then $\frac{du}{2} = dx$ and $x = \frac{u}{2}$ then if we sub that all in we have $n\int_0^2 \frac{u}{2} f''(u)\frac{du}{2}$ but if I instead do it with theorem 1.19 we have $k = \frac{1}{2}$ and we have $\int_0^2 tf''(t)dt = 2\int_0^1 tf''(2t)dt$ how is this discrepancy happening?
BigBen
@ornate sable Has your question been resolved?
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why is this the case. wouldnt the intergral measure area?
Then what would f do?
?
If the integral measures area of that circle, then how would a choice of f change anything?
What?
So this is a complex integral. You are integrating over the circle γ which lives in the complex plane.
On every point of the circle, there's a value of the function f(z).
We basically add up what the function is doing on every point of the circle. That's the answer to the integral.
to see that the integral need not have anything to do with area, try f = 0
I have no idea how to do that
I dont know what f(z) is
Its just supposed to be some function that gives an in closed space
f(z) is not that circle. f(z) is a function that lives on that circle. f(z) can be anything you want! (Kind of.)
f(z) = z² works. If you integrate that over that circle, you get 0.
Are you in a complex analysis course?
Not right now im trying to learn complex analysis tho
Can you explain how f(z) could equal z^2 I don't understand
f(z) is anything you want. It's a open slot for you to put a function in.
Then what does the circle mean
That's the space you're integrating over
Note the function exists on every point of the circle, but the function is not the circle itself
So it's like if you took a circle chunk out of the graph and looked at the function that was in the circle?
Wait how does it exist on every point of the circle?
Also sorry my phones at 1% lemme get too my computer ill be back in like 4 mins
back
is it every point in the circle or every point on the perimiter
also, the integral sign with circle usually denotes line integral
so it's over only the circle not the whole disk
so whats the difference between f(x) and the circle
f(x) is defined on the circle, circle is the domain
it's like defining some function (like x^2) on whole plane and then just looking at the portion of the function restricted to a circle
so it would be like 2 points on the circle?
In calc 1, you only integrate on the interval (a,b). All integrals are 1D lines, and you can put a function on them.
In complex analysis, you get to integrate over 2D shapes
Usually one takes calc 3 before complex analysis, in which 3 dimensional integrals often happen
thats just partial deriviation right?
no, do you know multvariable calculus or have you encountered multivariable functions in the past?
idk
like functions defined on plane, not just the real line
(so function with two variables)
so just like x+y=z type stuff yeh?
yeah, or f(x, y) = x+y
Well, f(z) = x + iy is possible
yeah i'm talking about real functions rn but that would be the complex equivalent
maybe this'll be easier, why do you think it's 2 points?
i still dont understand why this would be a higher order intergral? and why its 0
cuz a function would go through it at 2 points
to enter
and to leave
or 0 points sometimes
if it doesnt enter at all
or 1
if its tangent
okay, so you're thinking of a line/curve, which would be a function from real line to the space of interest
in this context z is a complex number, so the most natural way to visualize it is on the complex plane
yeah
so the function f is NOT a line
its a plane right?
not necessarily a plane but a surface
when taken over whole complex plane
and if it's real-valued but let's first just talk about real-valued ones
but how would a plane intersect a 2d circle? like i can imagine the z axiss being imaginary but isnt this situation still 2d?
it's not intersecting it
the plane/surface (so the function) is defined on some domain - the set you take input values from
either R^2 or C
the circle is a subset of that domain that carves some portion of the surface
you can imagine a surface floating over the real plane (so it's in the third "dimension")
and then you take a circle out of the real plane and look what shape it traces on the surface floating above it
that trace is the portion of the function defined on the circle, the thing you're integrating
wouldent a circle trace out a line on the surface
a curve yes, line no
i dont understand
you're looking from the wrong "above" tho
the circle is laying on a table
surface is floating above the table
and you look at what portion of the floating surface is directly above the circle
so would it be like a circle if u looked at it from above and it would have different hieghts when look at from the side
ok that makes sense
idk if the drawing helps but that's what i mean more or less, the arrow in the middle is going "to the back"
yup so that's the f(z) defined on a circle
although it's only the real one
so why wouldent the function matter when determining the intergral besides if theres poles
yeah so that's where complex numbers come in
this surface thingie is only the real part
and you have the imaginary part too
which complicates things
are you able to draw on the picture u made of what the intergral of that represents
or is it too complicated
You're asking for a 4D picture haha.
There's ways that can be done, like using color for the 4th dimension, but it's getting messy
