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**arze** I need to check that my work is correct for these transformation matrices.

A, a reflection in *Ox*. $\displaystyle \left(\begin{array}{cc}1&0\\0&-1\end{array}\right)$

B, an enlargement by a factor 2. $\displaystyle \left(\begin{array}{cc}2&0\\0&2\end{array}\right)$

C, a rotation by $\displaystyle \frac{\pi}{2}$ about *O*. $\displaystyle \left(\begin{array}{cc}0&-1\\1&0\end{array}\right)$

D, a stretch by a factor of 3 in the direction *Oy*. $\displaystyle \left(\begin{array}{cc}1&0\\0&3\end{array}\right)$

E, a reflection in the line y=x. $\displaystyle \left(\begin{array}{cc}0&1\\1&0\end{array}\right)$

Can someone help me see of they are correct?

Thanks