In 2-D, the 2x2 matrix is very simple. If you want to rotate a column vector v by t degrees using matrix M, use

M = {{cos t, -sin t}, {sin t, cos t}} in M*v.

If you have a row vector, use the transpose of M (turn rows into columns and vice versa). If you want to combine rotations, in 2-D you can just add their angles, but in higher dimensions you must multiply their matrices.