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# C4 Parametric Equations watch

1. Hi,

I'm stuck on this question. I think I know what to do - I just can't get the rearranging.

Q. Find the cartesian equation of the curve given that the parametric equations x = t + 1/t and y = t - 1/t

Do I just have to find dy/dx and then integrate ?

Thanks
2. If you found dy/dx it would be in terms of t, which doesn't really bring you any closer to the answer. I'd try and get something in the form t=... first, and then substitute into one or other of the equations. A good place to start would be to consider x+y.
3. try and then and see what you come up with.

If you still can't work it out:
Spoiler:
Show
4. I think I have got it.

Using difference of two squares, (x+y)(x-y) gives 4.

...so therefore (x^2)-(y^2) = 4 is the answer ?

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Updated: October 11, 2009
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