Question

From the diagram below, if AC is a tangent line, and if PD = 8 and DC = 9, find the length of BC.

Answer 1

Given,

PD = 8 and DC = 9

Required

The length of line BC.

Here, PB and PD are the ardius of the circle. By the definition of circle, the measure of all radius is equal.

So, PB = PD = 8.

The tangent is always perpendicular to the radius at the point of tanjency.

By the pythagoras theorem,

$\begin{gathered} PB^2+BC^2=PC^2 \\ 8^2+BC^2=(17)^2 \\ BC^2=289-64 \\ BC^2=225 \\ BC=15 \end{gathered}$

Hence, the measure of BC is 15 units.