You can
put this solution on YOUR website! Did you make two typos?
((cos2θ+isinθ)^4*(cos3θ+isin3θ)^5)/(cos7θ+isin7θ)^3*(cosθ-isinθ)
I think you meant
((cos2θ+isin2θ)^4*(cos3θ+isin3θ)^5)/(cos7θ+isin7θ)^3*(cosθ+isinθ)
If you meant a "2" and a "+" in those two places then I can show that the
answer is cos3θ+isin3θ. Otherwise it's a complicated mess.
Edwin