Circles

Find the magnitude of the angle that the diagonals $BE$ and $DH$ make in the regular nonagon $ABCDEFGHI$. (See the picture.)

Find the magnitude of the angle that the diagonals $AF$ and $CG$ make in the regular octagon $ABCDEFGH$. (See the picture.)

What is the measure of the angle made by two line-segments marked in the clock face (see the picture)? One segment is connecting points $7$ and $1$, second segment is connecting points $5$ and $10$.

What is the measure of the angle made by two line-segments marked in the clock face (see the picture)? One segment is connecting points $10$ and $2$, second segment is connecting points $5$ and $2$.