I will give you some hints, try them and see what you come up with
- put everything in terms of sine and cosine
- combine all terms into a single term (simplify)
weird question. start on the left hand side, expand it using the addition formula for sine. show that you can't get the right hand side from that2. Show that the equation sin(x+y)=sin x + sin y is not an identity.
the product to sum formula for sine-cosine is:3. Write the product 11sin (x/2) cos (x/4) as a sum.