Periksa apakah titik kiri atau kanan vektor

Check position of point M(X, Y) relative to vector AB with points A(Ax, Ay) and B(Bx, By):

position = sign((Bx - Ax) * (Y - Ay) - (By - Ay) * (X - Ax))

M is: 	+1 left,
		-1 right,
    	0 on the vector AB
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