$C$ is a point on the extension of diameter $A B, C D$ is a tangent, angle $A D C$ is $110^{\circ}$. Find the angular measure of arc $B D$.

#
The angle between the tangent and the chord is equal to half the angular measure of the arc enclosed between them.

## Solution

$$
\begin{gathered}
\cup D B A=2 \angle A D C=220^{\circ}, \\
\cup D B=\cup D B A-\cup A B=220^{\circ}-180^{\circ}=40^{\circ} .
\end{gathered}
$$

## Answer

$40^{\circ}$.