Explain step by step how you would evaluate cos(a+b) given the values of sin(a) and sin(b) both expressed as y/r, if both a and be are a part of the set interval [0/(pi/2] and a doesnt equal b

Answer 1

Given only sin a and sin b use the identities:

sin a = cos (π/2 - a)

sin b = cos (π/2 - b)

Then cos (a + b) =

[cos (π/2 - a)] [cos (π/2 - b)] - (sin a)(sin b)

Answer 2

Use the identity cos(u + v) = cos(u)cos(v)-sin(u)sin(v)

So here you get

cos(a + b) = cos(a)cos(b)-sin(a)sin(b)

Then work in the sin(a) and sin(b)