Question:

A curve has parametric equations

x = 3 cos2 t, y = sin 2t, 0 ≤ t < π.

(i) Show that

= $\displaystyle \frac{dy}{dx} = -\frac{2}{3}cot 2t$

(ii) Find the coordinates of the points where the tangent to the curve is parallel to the x-axis

Ok, the first bit i did no problem, but its the second part because the gradient must be 0 correct?

meaning cot 2t = 0

However you cannot do the inverse of this because when cot t = 0...its an asymptote...

Thanks for any help