To verify that the tangent at any point to a circle is perpendicular to the radius through that point of contact.
A line that touches the circle at a single point is known as tangent to a circle.
Fig. (A) Tangent to the circle
The distance from the centre of a circle to the outside edge. See Fig (B).
Fig. (B) Radius of the circle
Perpendicular lines are lines that intersect at a right (90˚) angle. See Fig (C).
Fig (C) Perpendicular angle
Shortest distance between a point and line is perpendicular distance.