In \(\triangle PQS\), \(R\) lies on \(PQ\) such that \(PR=RQ=RS\) and \(\angle QRS =z\degree\).
Determine the measure of \(\angle PSQ\).
Extension: Consider the circle with centre \(O\) and diameter \(AB\). Suppose point \(C\) is a point on the circumference of the circle other than \(A\) or \(B\). Determine the measure of \(\angle ACB\).
