| Exam Board | Edexcel |
| Module | C2 (Core Mathematics 2) |
| Year | 2014 |
| Session | January |
| Topic | Trig Equations |
9. (a) Show that the equation
$$5 \sin x - \cos ^ { 2 } x + 2 \sin ^ { 2 } x = 1$$
can be written in the form
$$3 \sin ^ { 2 } x + 5 \sin x - 2 = 0$$
(b) Hence solve, for \(- 180 ^ { \circ } \leqslant \theta < 180 ^ { \circ }\), the equation
$$5 \sin 2 \theta - \cos ^ { 2 } 2 \theta + 2 \sin ^ { 2 } 2 \theta = 1$$
giving your answers to 2 decimal places.