write cos(5x) Cos (3x) as a sum of trigonometric functions

Question

write cos5xcos3x as a sum of trigonometric functions

Answer 1

cosAcosB=(1/2)(cos[A+B]+cos[A-B])

cos(5x)cos(3x)=(1/2)(cos[5x+3x]+cos[5x-3x])

cos(5x)cos(3x)=(1/2)(cos(8x)+cos(2x))

cos(5x)cos(3x)=0.5cos(8x)+0.5cos(2x)