3 The curve \(C\) has polar equation \(r = \cos 2 \theta\), for \(- \frac { 1 } { 4 } \pi \leqslant \theta \leqslant \frac { 1 } { 4 } \pi\).
- Sketch \(C\).
- Find the area of the region enclosed by \(C\), showing full working.
- Find a cartesian equation of \(C\).