| Exam Board | Edexcel |
|---|
| Module | PMT Mocks (PMT Mocks) |
|---|
| Topic | Addition & Double Angle Formulae |
|---|
10. a. Show that
$$\sin 3 A \equiv 3 \sin A - 4 \sin ^ { 3 } A$$
b. Hence solve, for \(- \frac { \pi } { 2 } \leq \theta \leq \frac { \pi } { 2 }\) the equation
$$1 + \sin 3 \theta = \cos ^ { 2 } \theta$$