T1°T2 is a counterclockwise rotation about the origin by an angle of____rad

[nicknaq]

Let T1 be the reflection about the line 2x−3y=0 and T2 be the reflection about the line 2x+5y=0 in the euclidean plane.

- first I was asked to find the T1°T2 matrix. I did that.
- now I need to find the counterclockwise rotation about the origin of T1°T2

I should use http://en.wikipedia.org/wiki/Rotation_%28mathematics%29" matrix, right? Look beneath 'matrix algebra'.

What do I do..? I don't need step-by-step instructions. Just the general concept. Thank you

 

[Outlined]

You already computed you answer, the T1°T2 matrix! 2 reflections are a rotation.