For part a, consider cos 3θ = cos (2θ + θ). After which, we can apply Compound Angle/Addition Formula to prove.KiausuLormee wrote:Need help with this question

Solution: http://imgur.com/FBcE1gQ

For part b, we can use the result of part a to help us. Simplify both sides such that we can factorise and solve the equation like we normally do.

Solution: http://imgur.com/lxC3ZQ9