*the diagram shows a circle,centre O.the lines AB,BC and CA touch the circle at P,Q and R respectively. explain CQO=90 degrees *

The three lines AB,BC,CA are all tangent lines to the circle, and the circle is an inscriberd circle of the triangle ABC.

A tangent to a circle will touch it at one point only.

The tangent BC will touch the circle at the point Q.

O is the centre point of the circle.

OQ is a radius of the circle.

The radius of a circle to a point on the circle will always be perpindicular to the tangent at that point.

Hence, the radius OQ is perpindicular to the tangent BC.

i.e. **the angle OQC is 90ยบ**