calculate [R][S]

where R is the reflection matrix

[ 4/5 -3/5 ]

[-3/5 -4/5 ]

and S is the reflection matrix

[ -3/5 4/5 ]

[ 4/5 3/5 ]

i found [R][S] to be

[ -24/25 7/25 ]

[ -25/25 -24/25 ]

this is the hard part:

verify that it can be identified as the matrix of a rotation and determine the angle of rotation

try to make a picture illustrating how the composition of these reflections is a rotation