Show that, for any values of $x$ and $y$ where $x> y$,
1. the angle $SPQ$ is always the same and find this angle
2. the angle $SRQ$ is always the same and find this angle
3. the quadrilateral $SPQR$ is cyclic
4. the angle $PQR$ is always the same and find this angle
5. the angle $PSR$ is always the same and find this angle.