Question 377942
First we must show that triangles PKQ and PKR are congruent. PK is in both triangles, PQ = PR, and angle QPK = angle KPR (as PK is an angle bisector). Therefore, by SAS, the two triangles are congruent. This means that angle PKQ = angle PKR = 90 degrees (as the two angles are supplementary) so PK is perpendicular to QR.