1. Cos(30-x)= 2. Sin(3x-30)- sin(3x+60)=

jawab
1. cos (30-x) = cos 30 cos x + sin 30 sin x
= 1/2 √3 cos x + 1/2 sin x
= 1/2 (√3 cos x + sin x)

2. sin (3x-30) - sin (3x+60) =
= 2 cos 1/2 (3x-30+3x+60) sin 1/2 (3x -30 -3x - 60)
= 2 cos 1/2 (6x +30) sin 1/2 (-90)
= 2 cos (3x +15) . sin (-45)
= 2 cos (3x+15) . (-1/2 √2)
= - √2  cos (3x +15)