Here are some of the questions I'm stuck on.
1)Simply the expression:
this is what i have done and i cannot see where i have gone wrong.
answers says its cos(-y).why?
2)express sin(3x) in terms of sin(x). This questions follows on from the previous question which was asking to expand sin(x+2x) answer to this is .
3)Use the compound angle formulas and appropriate angles to find the exact value of .
This is what i have done:
book's answer is