Ans: A
By applying the cosine law to $\Delta ABD$, we have
By applying the cosine law to $\Delta ABD$, we have
$\begin{array}{rcl}
\cos \angle BAD & = & \dfrac{5^2 + 3^2 – 7^2}{2(5)(3)} \\
\cos \angle BAD & = & -0.5 \\
\angle BAD & = & 120^\circ
\end{array}$
Since $A$, $B$, $C$ and $D$ are points lying on the circle, we have
$\begin{array}{rcl}
\angle BCD + \angle BAD & = & 180^\circ \\
\angle BCD & = & 180^\circ – 120^\circ \\
& = & 60^\circ
\end{array}$
