3.5: Tangent from an external point to a circle

0606/22/F/M/25 — Question 1 · 8 marks

The diagram shows a circle with centre $O$ and radius $5\text{ cm}$.

The point $A$ lies on the circle.

The point $B$ is such that the line $AB$ is a tangent to the circle.

$OB$ has length $13\text{ cm}$.