#help-10

1 messages · Page 263 of 1

vast willow
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(-4,0) is this point on the drawn line

long plaza
obtuse pebbleBOT
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@long plaza Has your question been resolved?

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timid silo
obtuse pebbleBOT
timid silo
#

I don't understand this step

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the given proposition is that $\frac{a}{b} = \frac{c}{d}$

warm shaleBOT
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Mushaar

unique mural
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Hi

timid silo
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oh wait it's pretty simple

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nevermind

#

hi

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proper snow
#

For a given (false) claim and proof, what skills do you use to determine where the proof is false?

tardy epoch
proper snow
#

@tardy epoch

proper snow
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And A’ = A is complement and A\B = A - B @timid silo

tardy epoch
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yea counterexample would be fine here

proper snow
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I was thinking step 10

tardy epoch
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counterexample would be easier

proper snow
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Yes I know but I’m just trying to figure out where the proof is wrong

proper snow
obtuse pebbleBOT
#

@proper snow Has your question been resolved?

obtuse pebbleBOT
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@proper snow Has your question been resolved?

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timid silo
#

So why does “squaring the circle” exist

obtuse pebbleBOT
timid silo
tardy epoch
timid silo
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Like why

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Nor how

tardy epoch
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what

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you just repeated your question

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and ignored mine

timid silo
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Why is a circle bigger than a square that it fits in

timid silo
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I used “like”

tardy epoch
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🙄

timid silo
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What about the answer

tardy epoch
tardy epoch
tardy epoch
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that's different from squaring the circle

timid silo
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I might saying it wrong too

tardy epoch
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again, not answering my question

timid silo
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Whats it

tardy epoch
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what kind of answer

timid silo
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Like proof

tardy epoch
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what sort of proof

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like a picture should be good enough

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so draw the picture

timid silo
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I cant rn

tardy epoch
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then work on it when you can

timid silo
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Why am i a fucking dumbass

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Lot lot sorry for yalls effort

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.closr

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.closr

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.close

obtuse pebbleBOT
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sleek wadi
#

Is this solvable for f(x)?

obtuse pebbleBOT
sleek wadi
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Best I can get is this, but still cant integrate the left side from what I understand

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If it's not solvable, is there another way to find the parametrization for x^2 where the velocity is constant?

tardy epoch
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Looks separable

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,w solve dy/dx = 1/sqrt(1+4y^2)

tardy epoch
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Yea they give a function x in terms of y. Looks nearly impossible to invert

sleek wadi
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darnit

native inlet
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,w f'(x)sqrt(1-4f(x))=1

warm shaleBOT
native inlet
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W|A inverts it pretty well catthumbsup but I wouldn't solve what the separable gives algebraically

sleek wadi
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wait I tried wlfram alpha before and it said it didnt know lol

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Thanks for the help!

warm canopy
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Mrfancy is a wolfie whisperer

sleek wadi
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oh wait he forgot the squared lmao

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thats why it worked

tardy epoch
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,w f'(x)sqrt(1+4f(x))=1

native inlet
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oh damn I did kekw

tardy epoch
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Well I'll be damned

native inlet
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,w f'(x)sqrt(1-4f(x)^2)=1

warm shaleBOT
native inlet
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therree it is

sleek wadi
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ok, cool

native inlet
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yeah that looks nasty

sleek wadi
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yeah im not sure if the inverse works for what im doing, but I can try lol

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it's also only between -1/2 and 1/2 😭

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maybe the way I went about trying to find this was complicated, so I guess ill just explain the whole problem:

native inlet
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that's why you have the constant :)

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shift the constant the graph shifts

sleek wadi
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I wanna parametrize the equation y=x^2

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but with a constant speed

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And that's where that equation came from lol

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.close

obtuse pebbleBOT
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fervent meadow
#

I'm working through Shankar's textbook and am confused on how to proceed with this classical mechanics question (Ex. 2.7.8, (2)). We have been given an arbitrary point/coordinate transformation $$ q_i \rightarrow \bar{q}_i(q_1,..., q_n)$$ and we have already derived the equation $$ \bar{q}_i=\sum_j \frac{\partial q_i}{\partial\bar{q}_j}\dot{q_j}.$$ We want to show that $$ \left( \frac{\partial \dot{q}_i}{\partial{\dot{\bar{q}}}j} \right){\bar{q}} = \frac{\partial q_i}{\partial \bar{q}_j}.$$

So far I have that $$ \left( \frac{\partial \dot{q}_i}{\partial{\dot{\bar{q}}}j} \right){\bar{q}}= \left( \frac{\partial}{\partial \dot{\bar{q}}_j}\left[\sum_k \frac{\partial q_i}{\partial\bar{q}_k}\dot{qk} \right]\right){\bar{q}} $$ $$=\left( \sum_k \left[\frac{\partial q_i}{\partial\bar{q}_k}\frac{\partial \dot{\bar{q}}_k}{\partial \dot{\bar{q}}_j} + \dot{\bar{q}}_k \frac{\partial}{\partial{\dot{\bar{q}}_j}} \left( \frac{\partial q_i}{\partial\bar{q}k} \right)\right]\right){\bar{q}} $$ where I simply applied the product rule.

I am confused on how to continue, since isn't it possible that $\frac{\partial q_i}{\partial\bar{q}_k}$ can be a function of both $\bar{q}_j$ and $\dot{\bar{q}}_j$? Also, can someone please explain why it's important that we take the partial derivative with $\bar{q}$ held constant? Isn't holding $\bar{q}$ constant already implied by the partial derivative?

warm shaleBOT
#

thedude365

obtuse pebbleBOT
#

@fervent meadow Has your question been resolved?

obtuse pebbleBOT
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obtuse pebbleBOT
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formal inlet
obtuse pebbleBOT
formal inlet
#

this one asks to find the angle between 2 lines in R3

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I did the dot product over the 2 magnitudes

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aka this, which gives the angle

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however it states im doing this wrong

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i did -17/(sqrt(18)*sqrt(29))

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giving me an angle of 138.0792

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in the end

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(this is all in degrees)

obtuse pebbleBOT
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@formal inlet Has your question been resolved?

formal inlet
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<@&286206848099549185>

timid silo
formal inlet
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Take ur time

timid silo
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ok sorry for the hold up

timid silo
timid silo
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from the beginning

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we have two vectors

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d1 = (-3,4,-3) + t(-1,4,-1)

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and d2 = (0,0,-4) + s(3,-4,-2)

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and cosx = d1•d2/(||d1|| ||d2||)

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@formal inlet are you with me

formal inlet
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yes

timid silo
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ok now lets pick any values for s and t

formal inlet
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yeah ive had all this info is right so far

timid silo
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good

timid silo
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what do you pick?

formal inlet
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does it have to be 3 values each xyz?

timid silo
formal inlet
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then we could just do 0,0,-4 and 3,-4,-2 as tghey are both on the lines right

timid silo
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ok so you picked 1

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d2 = (0,0,-4) + (3,-4,-2)

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simplify this for me

formal inlet
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3, -4, -6

timid silo
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d1 = (-3,4,-3) + (-1,4,-1) and this too

timid silo
formal inlet
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-4, 8, -4

timid silo
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and d1= (-4, 8, -4)

formal inlet
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ahhh so I use these for the equation instead?

timid silo
timid silo
formal inlet
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cause I was just using s and t

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ok lemme get my calc

timid silo
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lemme do the same

formal inlet
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105.15043

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might have typed wrong

timid silo
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let me verify

timid silo
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what was your dot product?

formal inlet
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-20

timid silo
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ok same

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and the length of d1?

formal inlet
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uh lemme find

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isnt it magnitude?

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or is that the same thing?

timid silo
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ye

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||d1||

formal inlet
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sqrt(96)

timid silo
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and d2

formal inlet
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and d2 sqrt(61)

timid silo
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i got all of those too

formal inlet
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i still get same answer

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im in degrees if that matter

timid silo
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maybe my calculator is ded

timid silo
formal inlet
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either way the program accepts the answer

timid silo
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nic

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good job

formal inlet
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thanks for help 👍

timid silo
timid silo
formal inlet
#

.close

obtuse pebbleBOT
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timid silo
obtuse pebbleBOT
timid silo
#

what am i doing wrong here

latent walrus
#

it seems okay to me

timid silo
latent walrus
#

it might be because your lines end at -5 and 5, but i dont know if thats just the bound youre actually able to draw in

timid silo
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i think that might be the reason since ive clicked "Get a similiar question" multiple times and its always consistently 0.67 out of 2 when it says i get it wrong

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but i cant draw anything farther then -5 and 5 which is weird

daring rock
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have you used the third draw tool under the graph? it looks like it's for drawing rays

timid silo
#

oh my god i think that was the problem 😭

daring rock
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that makes sense cuz that score implies that it thinks only one part out of 3 is right

timid silo
#

yes

daring rock
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lol @latent walrus i'm amazed you noticed that, the difference in the picture is so tiny

timid silo
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ok thank you sm i think that was the problem

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obtuse pebbleBOT
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silk sparrow
#

I need some help w statistics

obtuse pebbleBOT
silk sparrow
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I am working on transformations

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of pmfs

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here is the problem:

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and here is my work

obtuse pebbleBOT
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@silk sparrow Has your question been resolved?

silk sparrow
#

no

slate zephyr
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What does pmf stand for

gilded needle
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probability mass function

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aka, p(x) = P(X = x)

slate zephyr
warm shaleBOT
obtuse pebbleBOT
#

@silk sparrow Has your question been resolved?

obtuse pebbleBOT
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silk sparrow
#

is that correct @slate zephyr ?

obtuse pebbleBOT
silk sparrow
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this is my work and a swer

slate zephyr
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yes

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you might want to be more clear than 1, 16, 81

silk sparrow
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1^4 , 2^4, 3^4,

slate zephyr
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you could say y is fourth power of integer for example

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or you could say that fourth root is an integer

silk sparrow
#

is my conclusion correct that the probability of X = positive is zero

slate zephyr
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no

silk sparrow
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lol

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Any suggestion on how I would go about doing that

slate zephyr
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sorry for the confusion

slate zephyr
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by definition X is negative integers

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but Y is positive integers

silk sparrow
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Okay so I just need to change my possible values for Y and state that y is a fourth power if an integer

slate zephyr
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*of

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what you wrote it correct

silk sparrow
#

thanks for taking the time to look into this and help me out! god willing I hope to be able to pay it forward (someday)

slate zephyr
#

but the sequence 1, 16, 81 is not particularly clear

silk sparrow
#

gotcha!

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obtuse pebbleBOT
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slate zephyr
#

you are welcome though

obtuse pebbleBOT
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round stag
#

apparently this is incorrect idk how

obtuse pebbleBOT
fierce lagoon
#

The -100

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Well

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Yeah that ain't right

shut lagoon
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You took +- once you isolated, but you have to take +- when you take the sqrt in the first place, then finish isolating

round stag
shut lagoon
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In particular, +-sqrt(A/P) = 1 + i/100 does not mean that +-(sqrt(A/P)-1) = i/100

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You did the second one

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But it is wrong

round stag
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so it should be..

shut lagoon
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It should be ... you that computes it

round stag
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just to confirm the postive side is right but not the negative

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correct?

shut lagoon
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Yes

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+- is attached to the sqrt

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Not the outside

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So your other one is ...

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cue

round stag
#

like so?

crude coral
#

isnt that the same answer u tried

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what he is trying to say is that
A/P = (1+(i/100))^2
+- sqrt(A/P) = 1+(i/100) this is correct

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the +- is only with the sqrt and not with the entire answer

round stag
#

should i remove the negative sign in front of 100 in the second answer? is that what you are referring to?
sorry my english isnt good.

obtuse pebbleBOT
#

@round stag Has your question been resolved?

round stag
#

.close

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dense crater
#

I have a question again

obtuse pebbleBOT
dense crater
#

Let's persay the 39# is considered point E

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Within this problem the professor actually used Position vecotr AD to compute the moment

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Can I use Position AE as Position Vector?

obtuse pebbleBOT
#

@dense crater Has your question been resolved?

dense crater
#

.close

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turbid charm
obtuse pebbleBOT
turbid charm
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.close

obtuse pebbleBOT
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floral remnant
obtuse pebbleBOT
floral remnant
#

I got here

royal basin
#

your handwriting is shit

floral remnant
#

I agree

royal basin
#

you have somehow managed to make the symbols a, 4 and 9 look identical

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anyway

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what is i^2?

floral remnant
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4i^2?

royal basin
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no, i^2 is not equal to 4i^2.

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answer my question.

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what is i^2?

floral remnant
#

Aaa, an algebraic expression?

royal basin
#

ok that's only technically correct.

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i is supposed to be the imaginary unit here.

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do you know what that is

floral remnant
#

Noooo...

royal basin
#

bruh

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i^2 = -1 ??

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you don't know this?

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you were not taught this?

floral remnant
#

Nooo lol

royal basin
#

bruh what

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how are you getting assigned this problem then

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if you do not even know what it says

floral remnant
floral remnant
royal basin
#

yes

floral remnant
#

I dont think that has anything to do with matrices in this problem lol

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They used i as an expression im 90% sure

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Okay wait lemme do that math using i as -1

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Holup

royal basin
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not i as -1

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i as sqrt(-1)

royal basin
#

but here this i is front and center in yours

floral remnant
#

Okay it worked but i dunno how to articulate this

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and the question hasent said anything about i being imaginary either 🤔

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Thanks anyways

#

.close

obtuse pebbleBOT
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timid silo
#

hi i had these two problems i needed help with

obtuse pebbleBOT
oblique nebula
#

What are those problems?

timid silo
#

Sorry it wasn’t uploading

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I am supposed to use dimensional analysis

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I do have a reasoning

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If we look at RHS, we see that dimension of [a] = [x] and Overall dimension of RHS is [a^n] or [x^n]

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On the right hand side, we’ll have the dimension would be [log x] which has to be dimensionless

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[a^n] = M^0 L^0 ^ T^0

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So n = 0?

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Is my reasoning correct?

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.close

obtuse pebbleBOT
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jaunty sluice
#

Is this the correct way to prove?

obtuse pebbleBOT
zenith spade
#

This is valid, yes

jaunty sluice
#

hurray!

#

thanks 😄

#

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exotic zealot
#

If f(x) is non-negative and it's sum over all its finite or countably infinite no. of x values in the domain is 1, then f(x) can serve as a probability mass function of a random variable X.

exotic zealot
royal basin
#

well like... you can just construct a random variable whose PMF is f(x), no?

exotic zealot
#

but how is that so apparent that the text just says "immediately" ?

royal basin
#

here's an example

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let $f(x) = \begin{cases} 0.1 & x=2 \ 0.4 & x=7 \ 0.35 & x=11 \ 0.15 & x=21 \end{cases}$

warm shaleBOT
exotic zealot
royal basin
#

the random variable X with this function as pmf
is the random variable which takes the value 2 with probability 0.1, 7 with probability 0.4, 11 with probability 0.35 and 21 with probability 0.15

#

that's it.

exotic zealot
#

can you please talk me through the three postulates that a probability measure/function has to satisfy in order for this to work? That is, to talk me through how this situation satisfies/we can make it satisfy the three axioms

exotic zealot
royal basin
#

you want to go down all the way to the axioms...?

exotic zealot
#

i mean if you're saying this is a random variable, then it has to have a vaild probability measure/the probability function P. right?

royal basin
#

sure i guess

exotic zealot
#

because an r.v. is defined on the basis of a sample space and a sample space is defined along with a probability function, as far as I understand

royal basin
#

formally a random variable is a measurable function from a sample space Ω to the real number line.

#

so like

#

to give you a sample space specifically tailored to our random variable

#

let Ω = {a,b,c,d}, F = 2^Ω, and the probability measure defined by assigning to the points a, b, c and d the weights 0.1, 0.4, 0.35 and 0.15

exotic zealot
#

ok..

royal basin
#

does this satisfy you or do you want to spend 3 hours wading through the formal proof that all the axioms are satisfied?

#

it's going to be very unenlightening.

exotic zealot
#

can you state the non-negativity axiom for me..?

royal basin
#

P(E) ≥ 0 for all events E

exotic zealot
#

do you just make the P defined to have the additive axiom?

exotic zealot
royal basin
#

but maybe you want me to list out all 16 values of P because you won't believe me otherwise.

exotic zealot
royal basin
#

...

#

i claimed X has that PMF

#

i haven't yes proved it

royal basin
#
P(∅) = 0
P({a}) = 0.1
P({b}) = 0.4
P({c}) = 0.35
P({d}) = 0.15
P({a,b}) = 0.5
P({a,c}) = 0.45
P({a,d}) = 0.25
P({b,c}) = 0.75
P({b,d}) = 0.55
P({c,d}) = 0.5
P({a,b,c}) = 0.85
P({a,b,d}) = 0.65
P({a,c,d}) = 0.6
P({b,c,d}) = 0.9
P({a,b,c,d}) = 1

here is the probability measure i define on my 4-point sample space

exotic zealot
#

but this does not satisfy the additive axiom

royal basin
#

you claim so?

exotic zealot
#

P{a,b} = P{a} +P{b}..

royal basin
#

yes/no question

exotic zealot
royal basin
#

ok, then give me a pair of events E and F, disjoint, s.t. P(E ∪ F) ≠ P(E) + P(F).

#

maybe i fucked up my arithmetic somewhere.

#

oh yes, i did.

#

hold on.

#

do you maintain your claim?

exotic zealot
#

you haven't edited it yet though..

royal basin
#

yes i have

exotic zealot
#

oh..ok

royal basin
#

do you claim that the measure P that i just wrote out in FULL doesn't satisfy additivity? Y/N

exotic zealot
#

no, I'm completely satisfied

#

but do you have an idea as to how you would prove this in general? I tried to but how is the proof so trivial still gets me.

royal basin
#

i mean like

royal basin
#

yes as in you DO claim it DOESNT satisfy additivity???

#

or what

exotic zealot
#

no..

royal basin
#

bruh

exotic zealot
#

i agree

#

this is valid

royal basin
#

ok

#

so like

#

anyway

#

let x_1, x_2, ... be the set of values at which f(x) > 0. by assumption this set is at most countable and so can be viewed as a sequence, whether finite or infinite.

exotic zealot
royal basin
#

construct a sample space Ω of as many points as needed

#

assert P({x_n}) = f(x_n)

#

then extend P by additivity

#

since $\sum_n f(x_n) = 1$ you will get $P(\Omega) = 1$ just fine

warm shaleBOT
exotic zealot
royal basin
#

there's no X yet.

exotic zealot
#

but P is a set function..

royal basin
#

i mean you can make the points in the sample space formally different from the numbers x_n

royal basin
exotic zealot
#

ok so you mean P{w_n} = f(x_n)?

royal basin
#

sure.

exotic zealot
#

ok..

royal basin
#

since you wanted to correct me so badly

#

on an inane and trivial point, i must add

#

but like

#

ok fine

#

P({w_n}) = f(x_n)

#

and then extend that by additivity to all subsets of Ω

#

and then X : Ω -> R will be defined by w_n ↦ x_n and it will have the required pmf

exotic zealot
#

so the additive extension guarantees that any subset will also probabilistically be non-negative , I guess?

royal basin
#

the probability of any subset will also be nonnegative

exotic zealot
#

on a personal note, do you really think this follows immediately though?

#

my doubt is cleared btw. Good explanation i must say

royal basin
#

because all of these constructions are... less intimidating than the notation might make them appear

exotic zealot
#

oh..have you seen other texts like this where they say immediately follows, but is even more not-so immediate than this?

#

do they get progressively more "skip obvious steps" and along with that, do you also get used to it?

royal basin
#

i guess so

exotic zealot
#

ok. thank you.

#

.close

obtuse pebbleBOT
#
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bright geyser
#

Yo i’m stuck trying to understand besides identity

bright geyser
#

bedouts

#

besouts

#

BESOUTS

#

BEZOUTS

#

this one

#

I understand that d will divide ax + by

#

but not that d = ax + by

#

would love some help

royal basin
#

there EXIST x and y such that ax+by is exactly d

#

if you want, give me two integers and i will tell you their GCD and a bézout expression for it

hasty salmon
#

You can look at the proof

bright geyser
bright geyser
#

i just coke across stuff like this that seemingly uses the proof to prove itself

bright geyser
#

it would just be helpful to work through a proof with someone

royal basin
#

brb

bright geyser
#

ight

royal basin
#

ok im back

#

so like do you want to work through a pre-written proof or do you want a demonstration with an example

bright geyser
royal basin
#

"this"?

#

which one would you like tho

bright geyser
#

whoops sorry

#

second one

#

demonstration with example

royal basin
#

ok

#

give me two integers

#

any two, but preferably ones not equal to each other nor zero

bright geyser
#

11 and 64

royal basin
#

ok, let's see...

#

gcd(64, 11) = 1 = 64 * 6 + 11 * (-35)

#

,calc 64 * 6 + 11 * (-35)

warm shaleBOT
#

Result:

-1
royal basin
#

oops

#

flip that

#

64 * (-6) + 11 * 35

#

is 1

bright geyser
#

hmm ok

#

maybe a full proof would help acyually

royal basin
#

do you have a proof that you're reading somewhere?

bright geyser
royal basin
bright geyser
#

ye sorry i’ll just be a few minutes

royal basin
#

ok

#

ping me once you can show me the proof

obtuse pebbleBOT
#

@bright geyser Has your question been resolved?

obtuse pebbleBOT
#
Channel closed

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royal basin
#

.reopen

obtuse pebbleBOT
#

royal basin
#

@bright geyser ya still there or what

bright geyser
#

sorryy, I think I actually found a proof

#

this one was a little strange but it did make sense to me

obtuse pebbleBOT
#

@bright geyser Has your question been resolved?

restive stratus
#

how to count the cos?

#

i forget

obtuse pebbleBOT
#
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#
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Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
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tranquil yarrow
obtuse pebbleBOT
restive stratus
#

no just cos

tranquil yarrow
#

?

restive stratus
#

in a triangle

tranquil yarrow
#

what?

royal basin
obtuse pebbleBOT
royal basin
obtuse pebbleBOT
# tranquil yarrow
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'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
keen garnet
#

!show

obtuse pebbleBOT
#

Show your work, and if possible, explain where you are stuck.

restive stratus
#

forgot about it

tranquil yarrow
#

i need to prove that the initial equation has no roots
and/or that my polynomial equation has no root in the interval [0; 1]

restive stratus
#

i ment the simple cos

royal basin
tranquil yarrow
#

yeah

royal basin
#

so that means t ranges from 0 to 1

tranquil yarrow
#

yes

royal basin
#

and from the graph you see the function has no zeros between 0 and 1

tranquil yarrow
#

exactly

restive stratus
#

how old are you

tranquil yarrow
#

but i cannot graph this on a piece of paper because it's too complicated

tranquil yarrow
restive stratus
#

say it

#

come on

royal basin
#

or are you just gonna keep interrupting

#

bc so far you've said nothing that was helpful or relevant to the question at handd

#

and OP's age is not relevant either

restive stratus
#

i am 13 you genius

#

how can i help you

royal basin
#

good for you but nobody asked your age

keen garnet
restive stratus
#

nnnnnn

royal basin
#

anyway ok so like

i need to prove that the initial equation has no roots
hm

tranquil yarrow
#

yeah

royal basin
#

can we come up w/ some clever bounds here

#

cos^6(x) + sin^8(x)

#

what can we do to this

tranquil yarrow
#

turn cos^2x into 1-sin^2x and vice versa

#

idk really

royal basin
#

wait

#

do you have access to double-angle identities and such

tranquil yarrow
#

ofc but why do i need them

#

the only thing i've come up with is to find the derivative, then determine the point where f(x) is the smallest

royal basin
#

overkill imo

tranquil yarrow
#

but as i said it didn't help due to me not being able to solve the cubic equation f'(t)=0

royal basin
#

oh this is EASY actually

tranquil yarrow
royal basin
#

$\sin^8(x) \leq \sin^2(x)$ and $\cos^6(x) \leq \cos^2(x)$

warm shaleBOT
royal basin
#

so lhs ≤ 1

tranquil yarrow
#

uhmmm interesting

#

but it doesn't prove anything

#

as far as i can see

#

i mean like

#

i understand what you mean but mathematically for this to mean something sin(x) and cos(x) have to be equally monotonic

royal basin
#

???

#

you don't need any monotony for shit

#

these two inequalities imply that FOR ALL REAL $x$ we have $$\sin^8(x) + \cos^6(x) \leq \sin^2(x) + \cos^2(x) = 1$$

warm shaleBOT
royal basin
#

therefore $\sin^8(x) + \cos^6(x) \leq 1$ for all $x$

warm shaleBOT
royal basin
#

but 5/4 is greater than 1

#

do you agree or disagree? @tranquil yarrow

fervent cradle
#

oh lol that's funny

#

trick question

tranquil yarrow
#

i agree with what you're trying to say but disagree with your conclusion

keen garnet
#

1>5/4 ?

tranquil yarrow
#

not that

royal basin
#

can you tell me what you disagree with

#

like quote me

tranquil yarrow
#

i know it's true but that's definitely not how you prove it

royal basin
#

for all real numbers $a, a', b, b'$ if $a \leq a'$ and $b \leq b'$ then $a+b \leq a'+b'$

warm shaleBOT
royal basin
#

agree or disagree?

tranquil yarrow
#

I agree but sin(x) and cos(x) are not constant numbers, they're functions

#

for every x in [0; 2pi] they vary

royal basin
#

this reasoning applies to them all the same just with a ∀x ∈ R stuck to the front

royal basin
keen garnet
#

can you find a value of x when $sin^8(x)>sin^2(x)$

warm shaleBOT
#

Joseph.P

tranquil yarrow
#

okay Ann i have a question for you

royal basin
#

hit me

tranquil yarrow
#

how do you prove $$2cos(x) + 5sin(x) = 8$$ has no solutions

warm shaleBOT
#

exterminated

royal basin
#

$|2 \cos(x) + 5 \sin(x)| \leq 2 |{\cos(x)}| + 5 |{\sin(x)}| \leq 2 \cdot 1 + 5 \cdot 1 = 7$

#

apply triangle inequality

warm shaleBOT
royal basin
#

or even simpler

keen garnet
#

or Caushy Swartz inequality

tranquil yarrow
#

its not because max(cos(x)) == max(cos(x)) = 1 right?

royal basin
#

what

tranquil yarrow
royal basin
#

i never spoke about maximum

tranquil yarrow
#

uhm okay

royal basin
#

sorry, can you restate your question to me

#

because it looks like you take issue with the proof i just presented but i do not know what your issue is

tranquil yarrow
#

yeah well okay

#

i agree

#

gj

obtuse pebbleBOT
#

@tranquil yarrow Has your question been resolved?

#
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#
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Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
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• Be polite and have a nice day!

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formal heron
#

what.. im lost and idk how to do any of those..

formal heron
#

Be it a , b > 0 . Demonstrate the unequals ?

#

the stuff inside () is just a few tips in order to help us

#

but idk anyhting

static marten
#

with the first question, how could you make the inequality easier to prove

formal heron
#

well i could multiply the 2 with the a2+b2 and the 1 with the shorted formula that i got below ?

#

or idk

static marten
#

which formula?

formal heron
#

since i could probably make the a2 + b2 into this form

formal heron
static marten
#

$2(a^2+b^2)\geq a^2+2ab+b^2$

warm shaleBOT
#

chlamydia

static marten
#

is this what you mean?

formal heron
#

yeah..

static marten
#

right, so where can we progress from here?
having terms on both sides of the inequality is a bit inconvenient

formal heron
#

sorry but what do you mean by terms ? since english is my second language i dont really understand a lot of stuff

static marten
#

all the a and b

formal heron
#

ah

formal heron
#

but idk if it'll head us towards a dead end or not

static marten
#

sure, so that gives us

#

$a^2+b^2-2ab\geq0$

warm shaleBOT
#

chlamydia

static marten
#

does this look familiar?

formal heron
#

i mean it does..

#

so we just redo the formula said previously?

#

and we end up with (a-b)^2 ?

static marten
#

$(a-b)^2\geq0$

warm shaleBOT
#

chlamydia

static marten
#

and because it's squared, it's always true

formal heron
#

wait that was it ?

static marten
#

what were you confused about

#

for a,b>0, that's all

formal heron
#

wait but how did we substarct the a and b from this and got this outcome ?

#

or

#

nvm

#

nvm

#

we moved the 2ab as well in that process

#

with the changed symbol

static marten
#

yeah

#

it works the same way as an equality, always change sign when moving it

formal heron
#

so what about doing 2 now ?

static marten
#

so what's the obvious problem in 2?

formal heron
#

so we could ^2 it all

#

or

static marten
#

sure

formal heron
static marten
#

$\frac{a^2+b^2}2\geq\frac{(a+b)^2}4$

warm shaleBOT
#

chlamydia

static marten
#

$2(a^2+b^2)\geq a^2+2ab+b^2$

#

oops

warm shaleBOT
#

chlamydia

static marten
#

you can see where i got this?

formal heron
#

we moved the 4 to the other side by multiplication

#

right ?

static marten
#

yeah, and expand (a+b)^2

formal heron
#

yeah

static marten
formal heron
#

now it is just like last problem.

#

a^2 + b^2 - 2ab >_ 0

#

i think

#

$a^2+b^2 - 2ab\geq 0

unique mural
#

Hi

static marten
#

$a^2+b^2 - 2ab\geq 0$

warm shaleBOT
#

chlamydia

formal heron
#

so this is also right ?

unique mural
#

Would you be free to help me out with a question

static marten
formal heron
#

alright , thanks

static marten
formal heron
#

the teacher gave a tip of " at end 2 can be given as a common factor"

#

what does that mean..

static marten
#

maybe it's talking about multiplying the 2 to simplify?

formal heron
#

probably

#

but we didnt need it

#

so it's alright

#

this is where i tried and failed so hard

#

but i'll try

static marten
#

did you square both sides

formal heron
#

ye

#

i squared it all

static marten
#

and you get a nasty right side

#

but because you have ab on both sides, you can do something with that first

formal heron
#

idk what we can do.. the only thing i thought of is multiplying both sides by (a+b)^2 to get rid of that from the right side

static marten
#

sure, but we can divide by ab too

formal heron
#

yeah that also but idk how to do that

static marten
#

$(a+b)^2\geq ab$

warm shaleBOT
#

chlamydia

static marten
#

why not

formal heron
#

since dividing was an option.. but how do we divide the terms?

#

i've never done this so idk how it's done

#

how do i divide 2a to a ? it'll give 2 ?

static marten
#

$ab\geq \frac{(ab)^2}{(a+b)^2}$

warm shaleBOT
#

chlamydia

static marten
#

what 2a

formal heron
static marten
#

oh yeah

formal heron
static marten
#

yes

formal heron
#

that's plausible but how do i do it tho

#

ab divided by ab = ?

static marten
#

because a,b>0, you can multiply or divide with no problem

static marten
formal heron
#

1

#

so i just write the result in numbers?

static marten
#

you are dividing (ab)^2 by ab here

formal heron
static marten
#

what do you mean?

formal heron
#

i dont understand how i can divide them since they aren't numbers

#

i know the principle but idk the way

static marten
#

i wouldn't say they aren't numbers, it's like they're pretending to be numbers

#

so ab represents a number

formal heron
#

but it is squared

static marten
#

yes

#

so you have a number squared divided by the number

formal heron
#

so do we get the root of that number?

#

the root of it**

#

like sqr ab ?

static marten
#

ok think of it this way

#

(ab)^2 can be expressed as (ab)*(ab)

#

right?

formal heron
#

yeah

static marten
#

so when you divide that by ab

formal heron
#

we get 1x1 ..

#

or?

static marten
formal heron
#

1*1

static marten
#

you only divide by ab once

formal heron
#

2?

static marten
#

like if you have 7^2 divided by 7

formal heron
#

it's 7

static marten
#

now pretend that ab=7

#

so (ab)^2 divided by ab

formal heron
#

so we get ab?

static marten
#

yes

formal heron
#

$ab\geq \frac{(ab)^2}{(a+b)^2}$

#

so we were here

warm shaleBOT
#

General.Admiral MWstudios

formal heron
#

so 1 >_ ?

static marten
#

we'll multiply the (a+b)^2 too

#

$(a+b)^2\geq ab$

warm shaleBOT
#

chlamydia

static marten
#

right?

formal heron
#

so we multiply it all by (a+b)^2

#

wait how did we go from a*b to (a+b)^2

#

oh

static marten
#

$1\geq\frac{ab}{(a+b)^2}$

#

from before

warm shaleBOT
#

chlamydia

formal heron
#

yeah

static marten
#

yup

formal heron
#

$(a+b)^2\geq ab$

warm shaleBOT
#

General.Admiral MWstudios

formal heron
#

then we simply move it to the left

static marten
#

i'll tell you now, you can't use the same trick

formal heron
#

then move it ?

static marten
#

$a^2+ab+b^2\geq0$

warm shaleBOT
#

chlamydia

static marten
#

nvm you can

#

because a,b>0, so all of it >0

formal heron
#

wait but

#

what happened to that ab

#

oh

#

nvm

#

nvm

static marten
#

it's ok

formal heron
#

so we simply - it from the expanded left side

#

since it was positive , we extracted it from the left row

#

right?

static marten
#

yes

formal heron
#

so we simply leave it as it is?

#

i mean we got what we wanted

static marten
#

yeah, there's no good way to factorise it

static marten
formal heron
formal heron
formal heron
static marten
#

same problem of square root

#

$(a+2)^2\geq2^2(a+1)$

warm shaleBOT
#

chlamydia

formal heron
#

so you but it all on ()^2 ?

static marten
#

yes

formal heron
#

so we get (a+2)^2 which is already a formula and it'll surely be used . on top of a+1

#

so it'll remain the same?

#

like we remove the a+1?

static marten
#

what do you mean remove

#

subtract?

formal heron
#

idk how we got rid of it

#

i mean we got (a+2)^2 on top from the ()^2 . but on the lower part we got a+1

static marten
#

$\frac{a+2}{\sqrt{a+1}}\geq2 \Rightarrow (a+2)\geq2\sqrt{a+1}$

warm shaleBOT
#

chlamydia

static marten
#

$(a+2)^2\geq 2^2(a+1)$

warm shaleBOT
#

chlamydia

formal heron
#

this is the first time i see someone move from the left to the right

static marten
#

it's not about left or right, it's about different things that make work hard, like fractions or square roots

formal heron
#

alright

#

it does make sense now

#

so now we simply open the left side

#

a^2+2ab+4 >_ 2^2(a+1)

static marten
#

woah

#

expand (a+2)^2 again

formal heron
#

i mean the formula is (a+b)^2 = a^2 + 2ab + b^2

static marten
#

yes

formal heron
#

so replacing that will be

static marten
#

and this time, b=2

formal heron
#

(a+2)^2 = a^2 + 2a2 + 2^2

#

OH DAMN

#

I put b

#

instead of 2

#

i just noticed it

static marten
#

oh lol

formal heron
#

so

#

a^2+ 4a + 4 ?

static marten
#

yeah

#

and the right side is?

formal heron
#

$a^2+4a+4\geq 2^2(a+1)$

warm shaleBOT
#

General.Admiral MWstudios

formal heron
#

so then..

#

wait

#

it gives us 4* a+1

#

so 4a + 4

static marten
#

yup

formal heron
#

so it gives us $a^2\geq 0$

warm shaleBOT
#

General.Admiral MWstudios

formal heron
#

right?

static marten
#

yes

formal heron
#

wth is that A.

static marten
#

this one is special, because you have a pattern

formal heron
#

yeah..

static marten
#

the upside down a?

formal heron
#

yeah

static marten
#

it means for all

formal heron
#

ah mb

static marten
#

$(t-\frac1t)^2\geq0$

warm shaleBOT
#

chlamydia

static marten
#

i want you to think about this

#

and see if you can get something nice out of it first

formal heron
#

i need to compare both of them

static marten
#

not yet

#

this is separate

formal heron
#

ah

static marten
#

you good?

formal heron
#

im stuck

#

i mean

static marten
#

did you expand the left?

formal heron
#

multiply it by t ?

#

..

#

no

#

OH DAMN

static marten
#

ah

formal heron
#

that's right

#

we could use that

#

t^2 - 2 * t * 1/t + t^2 >_ 0

#

right?

static marten
#

yeah

#

so about the 2t*1/t

#

that becomes 2, right?

formal heron
#

$2t*\frac1t$

warm shaleBOT
#

General.Admiral MWstudios

formal heron
#

i mean

#

wait 30 secs for me to process this

static marten
#

take your time

formal heron
#

yeah that's right

#

since if we replace t with any number other than 0

#

i mean greater than 0

#

it'll give us 2

#

for example 3

static marten
#

yeah, because you have t and you're dividing it away

formal heron
#

2* 3 multiplied by 1 and 3 it is 6 mult. 1/3 is 2

#

it's ilogical and logical at the same time

static marten
#

lol

#

so we have $t^2+\frac1{t^2}-2\geq0$

warm shaleBOT
#

chlamydia

static marten
#

$t^2+\frac1{t^2}\geq2$

warm shaleBOT
#

chlamydia

formal heron
#

so it is t+ 1 ?

#

or t^2 + 1

static marten
#

what do you mean

formal heron
#

dont we uhm

#

like add the t^2 to the 1/t^2

static marten
#

oh, don't worry about that

formal heron
#

and get t^2 + 1 / t^2

static marten
#

if we look back at the question

formal heron
static marten
#

$(x+1)+\frac1{x+1}\geq2$

formal heron
#

..

static marten
#

do you see something similar?

warm shaleBOT
#

chlamydia

formal heron
#

damn.

static marten
#

for positive numbers

formal heron
formal heron
#

damn

#

so (x+1)+1 / x+1

#

it is 1+1 ?

#

so 2..

static marten
formal heron
#

x

static marten
#

so we use that to make something useful

#

are you struggling?

formal heron
#

a bit..

#

since i havent done math in 3 months and i just started highschoolk

formal heron
#

or multiply it all by x+1

static marten
#

multiplying would be better

#

it should still work out

formal heron
#

yeah it'll be easier..

static marten
#

yeah maybe it wasn't good to try to teach that

formal heron
#

try to teach what

static marten
#

we could've just done multiplying

#

but that comes in useful for harder questions

formal heron
#

$(x+1)+\frac1{x+1}\geq2 | * (x+1)$

#

so we end up with

#

nvm

#

multiplying mbb

warm shaleBOT
#

General.Admiral MWstudios

formal heron
#

$(x+1)^2+\frac1(x+1){(x+1)^2}\geq2*(x+1)$

#

or.

#

wait

static marten
#

about the middle term

formal heron
#

i noticed it as well

warm shaleBOT
#

General.Admiral MWstudios

formal heron
#

wait wtf

static marten
#

use {(x+1)}

#

$(x+1)^2+\frac1{x+1}(x+1)\geq2(x+1)$

warm shaleBOT
#

chlamydia

static marten
#

right?

formal heron
#

ah yes

static marten
#

so you have x+1, and you're dividing by itself

formal heron
#

so we get 2 ?

static marten
#

please think carefully about this, if you have a number, and you divide by the same number...

formal heron
#

we get 1 ?

static marten
#

yeah

formal heron
#

nvm

#

we multiplied the 1 with the x+1 ?

covert kettle
#

pls where can i find help 0

formal heron
#

so we got x+1 / x+1?

static marten
#

yeah

formal heron
static marten
#

she already has a channel open lol

formal heron
#

that's alright

formal heron
formal heron