
Jared G. answered 08/08/15
Tutor
4.9
(221)
Math and Physics from Elementary to University
This isn't a hard problem once you understand matrix rotations.
Where [A]x[r]=[B]
[A] -is the original matrix
[r] - is the rotation matrix and
[B] -is the rotated or final matrix
in 2 dimensions
[r]= [cos(θ), sin(θ)
-sin(θ), cos(θ)]
Your point (4,-9) would just be the matrix [A]= [4, -9]
Since counterclockwise is the positive direction you just use θ=150 in the [r] matrix and the do the cross product of [A]x[r]. The result will be the rotated location of your point (or vector).
Abhay G.
08/09/15