
theta
How do I express cos3 theta in terms of sin theta?
So far I GOT
=cos (2 theta + theta)
=cos 2 theta cos theta  sin 2 theta sin theta
=((2(1sin^2 theta))1)cos theta  sin 2 theta sin theta
=((22sin^2 theta)1)cos theta  sin 2 theta sin theta
Now..... how do I eliminate the cos theta in order for it to become all sin theta
And
How do I solve this sin5 theta
So far I GOT
=sin(2 theta + 3 theta)
=sin 2 theta cos 3 theta + cos 2 theta sin 3 theta
=(2sin theta cos theta)(4 cos^3 theta  cos theta)+(12sin^2 theta)(3sin theta4ain^3theta)
I want to know how to express cos 3 theta in terms of sin theta in order for me to solve, I think, sin 5 by substitution theta.Please help me also how to simplify the expression sin 5 theta.
thanks
My edit: Added "by substitution"

Link
Try reading about these: Chebyshev Polynomials.
Kevin C.
