How do you write the expression cos25^circcos15^circ-sin25^circsin15^circcos25∘cos15∘−sin25∘sin15∘ 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!
