Find $\displaystyle \int\sin^2 (3x+2) dx $

and also another qn which i am not sure it belong to which catagory so i just post it here together with the previous qn.

the cubic polynomial is such that the coefficient of $\displaystyle x^3$is -2 ans the roots of the eqn f(x)=0 are 0.5,2 and k

Given that f(x) has a remainder -20 when divided by (x+2), find the value of k.

thank you