If the sides of a quadrilateral touch a circle. Prove that the sum of a pair of opposite sides is equal to the sum of the other pair.

The common point of a _____ and the circle is called the point of tangency.

A tangent to a circle intersects it in _____ point(s). ( Write answer in words)

A line intersecting a circle in two points is called a _____.

The angle between the tangent at a point on a circle and the radius through the point is _____$°$. 

In figure, $\mathrm{CP}$ and $\mathrm{CQ}$ are tangents to a circle with centre $\mathrm{O}$. $\mathrm{ARB}$ is another tangent touching the circle at $\mathrm{R}$. If $\mathrm{C}\mathrm{P}=11 \mathrm{c}\mathrm{m}$ and $\mathrm{B}\mathrm{C}=7 \mathrm{c}\mathrm{m},$ then find the length of $\mathrm{BR}$.

In, figure, $\mathrm{CP}$ and $\mathrm{CQ}$ are tangents from an external point $\mathrm{C}$ to a circle with centre $\mathrm{O}$. $\mathrm{AB}$ is another tangent which touches the circle at $\mathrm{R}$. If $\mathrm{CP}=11 \mathrm{cm}$ and $\mathrm{BR}=4 \mathrm{cm}$, if the length of $\mathrm{BC}=k\mathit{ }\mathrm{cm}$, find $k$.