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!
