The point of intersection of two diameters of a circle is not always the centre of a circle.

Find the following unknown angles.

Find the following unknown angle.

Find the following unknown angles.

Two tangents $PA$ and $PB$ are drawn from an external point $P$ to a circle with centre $O$. Prove that $PR=PA+AQ$

If the length of tangent drawn to a circle of radius $7 \mathrm{cm}$ from a point at a distance $25 \mathrm{cm}$ from the centre is $k \mathrm{cm}$, then find the value of $k$.

Find $x$, if $O$ is the centre of the circle.

Find $x$ and $y$ if $O$ is the centre of the circle.