5 The parametric equations of a curve are
$$x = \cos 2 \theta - \cos \theta , \quad y = 4 \sin ^ { 2 } \theta$$
for \(0 \leqslant \theta \leqslant \pi\).
- Show that \(\frac { \mathrm { d } y } { \mathrm {~d} x } = \frac { 8 \cos \theta } { 1 - 4 \cos \theta }\).
- Find the coordinates of the point on the curve at which the gradient is - 4 .