1956 AHSME Problem 10

A circle of radius 10 inches has its center at the vertex C of an equilateral \triangle ABC and passes through the other two vertices. The side AC extended through C intersects the circle at D. The number of degrees of \angle ADB is:

\textbf{(A)}\ 15^{\circ} \qquad \textbf{(B)}\ 30^{\circ} \qquad \textbf{(C)}\ 60^{\circ} \qquad \textbf{(D)}\ 90^{\circ} \qquad \textbf{(E)}\ 120^{\circ}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.