Question

Find length of a tangent drawn from a point 13cm from centre of a circle of radius 12cm.

Answer 1

Pythagoras' Theorem, r^2 = 13^2 -12^2 (because a tangent to a circle is perpendicular to the line joining the meeting point of the tangent to the centre)= 169–144 =25 = 5^2. Hence r = 5 cm. Therefore the diameter of the circle = 2×5 = 10cm.