`cos(3x)cos(2y) + sin(3x)sin(2y)` Write the expression as a sine, cosine, or tangent of an angle.

You need to recognize the formula `cos(a-b) = cos a*cos b + sin a*sin b` . You need to put `a = 3x ` and `b = 2y` , such that:

`cos 3x*cos 2y + sin 3x*sin 2y = cos (3x - 2y)`

Hence, the given expression could be evaluated as the cosine of the sum of angles 3x and 2y, such that `cos 3x*cos 2y + sin 3x*sin 2y = cos (3x - 2y).`

You need to recognize the formula `cos(a-b) = cos a*cos b + sin a*sin b` . You need to put `a = 3x ` and `b = 2y` , such that:

`cos 3x*cos 2y + sin 3x*sin 2y = cos (3x - 2y)`

Hence, the given expression could be evaluated as the cosine of the sum of angles 3x and 2y, such that `cos 3x*cos 2y + sin 3x*sin 2y = cos (3x - 2y).`