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Rotate 90 counter clockwise about the origin 

 Oct 15, 2015
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Rotate 90 counter clockwise about the origin 

 

\(\begin{array}{rcl} \dbinom{x_p}{y_p}\cdot \begin{pmatrix} \cos{(90)} & \sin{(90)}\\ - \sin{(90)} & \cos{(90)} \\ \end{pmatrix}\\\\ = \dbinom{x_p}{y_p}\cdot \begin{pmatrix} 0&1\\ -1& 0\\ \end{pmatrix}\\\\ =\dbinom{-y_p}{x_p} \end{array} \)

 

laugh

 Oct 16, 2015

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