In the given figure,if $\angle AOB = 125^{\circ}$,then $\angle COD$ is equal to: (in $^{\circ}$)

In the following figure,find $m \angle PBA$.

In $Fig.$,$AB$ and $CD$ are common tangents to two circles of unequal radii. Prove that $AB = CD$.

In the following figure,find the radius of the circle.

If $AB$ is a chord of a circle with centre $O$,$AOC$ is a diameter and $AT$ is the tangent at $A$ as shown in the figure. Prove that $\angle BAT = \angle ACB$.

Two tangents $PQ$ and $PR$ are drawn from an external point $P$ to a circle with centre $O$. Prove that $QORP$ is a cyclic quadrilateral.