The Student Room Group

Conics

Let C be the conic section with equation 3x^2-2root3 xy +y^2 +16x + 16root3 y=0

Find a value of alpha such that the coefficient of Xy in the equation for C in X & Y coordinates=0

So what I did is this

tan2alpha= -2root3/3-1 which gives me alpha as -pi/6 which is wrong though :/
Original post by Yiuyu
Let C be the conic section with equation 3x^2-2root3 xy +y^2 +16x + 16root3 y=0

Find a value of alpha such that the coefficient of Xy in the equation for C in X & Y coordinates=0

So what I did is this

tan2alpha= -2root3/3-1 which gives me alpha as -pi/6 which is wrong though :/


Could you post the whole question?
Reply 2
What do you think the right answer is? For such questions there is more than one right answer.
(edited 6 years ago)
Reply 3
Original post by BuryMathsTutor
Could you post the whole question?


Thats the question? It also says find the equation?
Reply 4
Original post by RichE
What do you think the right answer is? For such questions there is more than one right answer.


Well -pi/6 doesnt seem right to me personally so any hints?
Reply 5
Original post by Yiuyu
Well -pi/6 doesnt seem right to me personally so any hints?


Based on what? It looks right to me.
Original post by Yiuyu
Thats the question? It also says find the equation?


A rotation of pi/6 will give you the parabola with equation y=x28y=-\frac{x^2}{8} unless I messed up on my algebra.

I could explain the method I used tomorrow if you're still stuck.

I still say you didn't post the whole question though. :tongue:

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