Question

urgent please if somebody can help me with this equation (1) sin(α - β) cos(α + β) = sin α cos α - sin β cos β ) thank you

Answer 1

well you need to use the expansions

sin(A - B) = sin(A) cos(B) - cos(A)sin(B)

and then

cos(A + B) = cos(A) cos(B) - sin(A) sin(B)

multiply the 2 together and you'll get the right hand side after collecting like terms.

Answer 2

thanks cmapbell_st