Prove that the perpendicular at the point of contact to the tangent to a circle passes through the centre.

A tangent to a circle intersects it in _____ point(s). [Answer in words]

In the figure given below, if $\mathrm{}\mathrm{T}\mathrm{P}$ and $\mathrm{}\mathrm{T}\mathrm{Q}$ are the two tangents to a circle with centre $\mathrm{}\mathrm{O}$ so that $\mathrm{\angle }\mathrm{}\mathrm{P}\mathrm{O}\mathrm{Q}={110}^{\mathrm{o}}$, then $\mathrm{}\mathrm{\angle }\mathrm{}\mathrm{P}\mathrm{T}\mathrm{Q}\mathrm{}$ is equal to