# How do you write the expression #cos25^circcos15^circ-sin25^circsin15^circ# as a sine, cosine or tangent of an angle?

##### 1 Answer

Jun 5, 2018

#### Explanation:

Recall that

#cos(A + B) = cosAcosB - sinAsinB#

Therefore

#cos25˚cos15˚ - sin25˚sin15˚ = cos(25˚ + 15˚) = cos(40˚)#

Hopefully this helps!