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    find cartesian

    x =sint , y=cos2t

    is mine correct

    x = root (1/2 - y/2)

    the root means that the 1/2 - y/2 is in root
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    (Original post by otrivine)
    find cartesian

    x =sint , y=cos2t

    is mine correct

    x = root (1/2 - y/2)

    the root means that the 1/2 - y/2 is in root
    Yes though the equation looks much nicer with y the subject - its probably also quicker to get to . . .
    \cos(2t) = \ 2\times sin^2(t) - 1
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    (Original post by otrivine)
    find cartesian

    x =sint , y=cos2t

    is mine correct

    x = root (1/2 - y/2)

    the root means that the 1/2 - y/2 is in root
    I would use the double angle formula to expand y and write it in terms of x - then you don't have any horrible square roots to worry about!
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    (Original post by otrivine)
    find cartesian

    x =sint , y=cos2t

    is mine correct

    x = root (1/2 - y/2)

    the root means that the 1/2 - y/2 is in root
    Just another hint:
    \frac{y+1}{2}=\frac{1+\cos 2t}{2}=\cos^2 t
    so
    x^2 + \frac{y+1}{2}=1
    arranging
     y=-2x^2-1
 
 
 
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