Question

any ideas? Im clueless...

Express
cos(x + y) and sin(x + y)
in terms of sin x, cos x, sin y, cos y.

thanks

Answer 1

hints:

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

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

Answer 2

thanks jim_thompson5910 : )

Answer 3

you're welcome