A tangent meets a circle at one point and one point only.
The angle between a tangent and a radius is a right angle of .
In this diagram C is the centre of the circle and PT is a tangent to the circle.
CT = 5 cm and PT = 12 cm.
What is the length of CP?
PT is a tangent and CT is a radius, therefore .
We have a right-angled triangle, so we can use Pythagoras: