(a)[3]
Prove that triangle $OAP$ is congruent to triangle $OCQ$. State a reason for each statement you make.
(b)[2]
If obtuse angle $COA=140^\circ$ is given, find angle $QCO$.
Mathematics 4024 · O Level · Circle theorems I
Circle theorems I — practice question
$A$, $B$ and $C$ lie on the circle with centre $O$, and $AB=BC$. $P$ is the midpoint of chord $AB$ while $Q$ is the midpoint of chord $BC$.