Circles

Give the measure of the angle contained by two line segments with the endpoints at the numbers $7$, $8$ and $8$, $10$ on a clock face. (See the picture.)

What is the measure of the angle contained by two line segments: the first joining numbers $8$ and $11$, and the second joining numbers $11$ and $2$, on a clock face? (See the picture.)

Given a regular pentagon with the side $a$, find the radius $\rho$ of the circle inscribed to this pentagon.

A circle is circumscribed to the regular octagon. The perimeter of the octagon is $16\mathrm{cm}$. Find the radius of the circle and round the result to two decimal places. (The regular octagon is a polygon which has eight sides of equal length. The perimeter of the octagon is the sum of the length of all eight sides.) Circle circumscribed to the regular octagon.