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Mathematics 27 Online
OpenStudy (dls):

Need help finding asymptotes of curve!

OpenStudy (dls):

\[\LARGE y^2(x-2a)=x^3-a^3\]

OpenStudy (dls):

@ganeshie8

OpenStudy (dls):

@dan815

OpenStudy (dan815):

difference of cubes

OpenStudy (dls):

eh?

OpenStudy (dan815):

x^3 - a^3 = (x-a)(x^2 +xa + a^2)

OpenStudy (dls):

yep right

OpenStudy (dls):

so what difference does it make?

OpenStudy (dan815):

asymptote is a line that approaches a given curve but does not meet it at at any finite distance

OpenStudy (dls):

yep

OpenStudy (perl):

take the implicit derivative

OpenStudy (perl):

Given y^2(x-2a) = x^3 - a^3 2 y * y ' (x-2a) + y^2 ( 1) = 3x^2 solve for y '

OpenStudy (dan815):

ooo

OpenStudy (perl):

y' = ( 3x^2 - y^2 ) / (2 y * (x-a))

OpenStudy (perl):

you have horizontal asymptote when y ' = 0 (numerator = 0) , and vertical asymptote when y ' is undefined (denominator = 0 )

OpenStudy (dls):

The approach I Follow is: The variables having nth degree,I replace x with 1 and y with m and solve for phi n(m) and equate it to 0 \[\Large \phi_n (m)= 0\] this gives em some values of m...lets assume they are distinct. The value of c is given by : \[\Large c =\frac{ - \phi_2(m)}{\phi_3'(m)}\] then y=mx+c just in case if someones has heard of a method like this.... but im not getting answer by this method

OpenStudy (dls):

^^im assuming nth degree to be 3 here,so 2 is n-1..actual formula is -phi(n-1)/phi ' (n)

OpenStudy (dan815):

what about y=mx+b asymtotes

OpenStudy (dan815):

how about taking y'' and saying as they approach the asymtotes the change is approaching 0

OpenStudy (dls):

@perl > the answer is r sin theta=a i don't think we would get something like that

ganeshie8 (ganeshie8):

which is same as y = a hmm

OpenStudy (dan815):

yes

OpenStudy (dls):

I am actually looking to solve these particular types of questions involving r and theta. The next question is also similar, \[\Large r \theta=a\]

ganeshie8 (ganeshie8):

but isnt it strange that to have question in rectangular and answer in polar ?

OpenStudy (dls):

yep that's what strange..the next 5-6 questions have the same pattern!

ganeshie8 (ganeshie8):

using ur formula im getting m=1 for the slant asymptote

ganeshie8 (ganeshie8):

\[y^2(x-2a)=x^3-a^3 \implies \left(\dfrac{y}{x}\right)^2 \left(1-\dfrac{2a}{x}\right) = 1 - \dfrac{a^3}{x^3}\] taking the limit \(\large x\to \infty\) : \[\lim\limits_{x\to\infty} \left[ \left(\dfrac{y}{x}\right)^2 \left(1-\dfrac{2a}{x}\right) = 1 - \dfrac{a^3}{x^3}\right]\] \[\left(m\right)^2 \left(1-0\right) = 1 -0\]

ganeshie8 (ganeshie8):

that gives you \(\large m = \pm 1\) you still need to find \(c\)

ganeshie8 (ganeshie8):

so looke like you will be having 2 slant asymptotes

ganeshie8 (ganeshie8):

you already have vertical/horizontal asymptotes from perl's work right ?

OpenStudy (dls):

i dont think it will be done using this method :/ we don't involve polars

ganeshie8 (ganeshie8):

you want to work it in polar coordinates is it ?

OpenStudy (dls):

to reach the final answer...:P

ganeshie8 (ganeshie8):

can you use more words, im having hard time figuring out what exactly are u looking for :O

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