2025 IGCSE Additional Mathematics May/June 0606/23 Q12

The function \(\mathrm f\) is defined by \(\mathrm f(x)=15\cos^2(3x+1.5)+7\sin(3x+1.5)-13\) for \(-0.3\le x\le0.5\), where \(x\) is in radians.

1. Solve the equation \(\mathrm f(x)=0\).[5]
2. Find the \(x\)-coordinates of the two stationary points on the curve \(y=\mathrm f(x)\).[5]