Answer
$$5\cos3x\cos2x=\frac{5}{2}(\cos 5x+\cos x)$$
Work Step by Step
$$A=5\cos3x\cos2x$$
The product-to-sum identity that will be applied here is $$\cos X\cos Y=\frac{1}{2}[\cos(X+Y)+\cos(X-Y)]$$
Therefore, A would be $$A=5\times\frac{1}{2}[\cos(3x+2x)+\cos(3x-2x)]$$ $$A=\frac{5}{2}(\cos 5x+\cos x)$$
