Express $$5\cos x-12\sin x$$ in the form $R\cos(x+\alpha)$, where $R0$ and \(0^\circ&lt

Question

Express $$5\cos x-12\sin x$$ in the form $R\cos(x+\alpha)$, where $R>0$ and $0^\circ<\alpha<90^\circ$.

Accepted Answer

$13\cos(x+67.4^\circ)$.

Trigonometry