Question

Question #49c6e

Answer 1

Re-write the left side of the expression.:
1 - (cos 5x.cos 3x + sin 5x.sin 3x) =
The expression in parentheses is equal to cos (5x - 3x) = cos 2x.
We get the popular trig identity:
`1 - cos 2x = 2sin^2 x`

Reminder: Trig identity:
cos (a - b) = cos a.cos b + sin a.sin b