In ∆PQR, PR > PQ, PA is the bisector of angle P and PM is perpendicular to QR. Prove that angle APM = 1/2 ( angle Q - angle R).
PQR is a right-angle triangle right angled at Q. XY is parallel to QR. PQ = 6 cm and PX : XQ = 1: 2. Calculate the lengths of PR and QR.