5 The function f is such that \(\mathrm { f } ( x ) = a - b \cos x\) for \(0 ^ { \circ } \leqslant x \leqslant 360 ^ { \circ }\), where \(a\) and \(b\) are positive constants. The maximum value of \(\mathrm { f } ( x )\) is 10 and the minimum value is - 2 .
- Find the values of \(a\) and \(b\).
- Solve the equation \(\mathrm { f } ( x ) = 0\).
- Sketch the graph of \(y = \mathrm { f } ( x )\).