Jared G. answered • 08/08/15

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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