I don't see what your problem has to do with projections. Do you just want to find the images of the three vectors under a rotation of -30 degrees?
The matrix in 1. rotates vectors -30 degrees, right. You don't need the matrix in 2. for anything.
The way the matrix rotates a vector is simply by multiplying the matrix with the vector, so to see where (-3,2) gets rotated, you multiply the matrix in 1. with the column vector
in that order.