The exression

Question

sin(x+y) - sin(x-y) is equal to...

Answer 1

Use the double angle identity:  sin(u±v) - sinu cosv ± cosu sinv

 

sin(x+y)-sin(x-y)

 

= sinx cosy + cosx siny - [sinx cosy - cosx siny]

 

= 2 cosx siny