Theorem :Tangent and radius of a circle are perpendicular to each other.
A circle with centre O.
AB is the tangent to the circle at point B
and OB is the radius of the circle.
R.T.P. OB ⊥ AC
1. OB < OC || Since each point of the tangent other than point B is outside the circle.2. Similarly it can be shown that out of all the line segments which would be drawn from point O to the tangent line AC, OB is the shortest.3. OB ⊥ AC || The shortest line sgement drawn from a given point to a given line , is ⊥ to the line.