Question

Sederhanakan cos (100 + x) cos 10 - x + sin 100 + x sin 10 - x

Answer 1

Cos A Cos B + Sin A Sin B = Cos (A-B)
Cos (100+x) Cos (10-x) + sin (100+x) sin (10-x)

cos ({100+x} - {10-x})
cos(100-10+x+x)
cos(90+2x)
-sin(2x)