In the diagram, $AC$ is a diameter of the circle with centre $O$. $ACD$ is a straight line and

Question

In the diagram, $AC$ is a diameter of the circle with centre $O$. $ACD$ is a straight line and $AB=BD$. Prove that $BC=DC$, $\angle BAC=30{}^\circ $.

Accepted Answer

(a) Proved: $BC=DC$ (b) $\angle BAC=30^\circ$

Proofs in Plane Geometry