12 The equation \(x ^ { 3 } - 2 x ^ { 2 } - x + 2 = 0\) has three roots. One of the roots is 2
12
- Find the other two roots of the equation.
12
- Hence, or otherwise, solve
$$\cosh ^ { 3 } \theta - 2 \cosh ^ { 2 } \theta - \cosh \theta + 2 = 0$$
giving your answers in an exact form.