Answer :
Answer:
[cos(10x) - cos(8x)]/2
Step-by-step explanation:
sin(-x) sin(9x) = {cos[9x - (-x)] - cos(9x + (-x)]}/2
= [cos(10x) - cos(8x)]/2
Answer:
[cos(10x) - cos(8x)]/2
Step-by-step explanation:
sin(-x) sin(9x) = {cos[9x - (-x)] - cos(9x + (-x)]}/2
= [cos(10x) - cos(8x)]/2