If in doubt, \(k\cos (x - \alpha )\) usually works. These worked examples show the processes you'll need to go through to rewrite an expression in this form. Write \(2\sin x^\circ + 5\cos x^\circ ...

Given any expression of the form \(a\cos x + b\sin x\) it is better to rewrite it into one of the forms \(k\cos (x \pm \alpha )\) or \(k\sin (x \pm \alpha )\) before answering the question.