trig
posted by Kate .
write an equation expressing 19cos(theta50degrees) as a sum of sine and cosine.

Using the identity cos(ab) = cos a cos b + sin a sin b
cos(θ50) = cosθcos50 + sinθsin50
= .64cosθ + .77sinθ
so,
19cos(θ50) = 19(.64cosθ + .77sinθ)
= 12.16cosθ + 14.63sinθ