Summary1. The common point of the tangent and the circle is called the point of contact.
2. A tangent to a circle is perpendicular to the radius through the point of contact.
3. A tangent to a circle is a special case of the secant, when both the end points of the corresponding chord coincide.
4. Only one tangent can be drawn through a point on a circle.
5. No tangent can be drawn through a point lying inside the circle.
6. Two tangents can be drawn through a point lying outside the circle.
7. The lengths of the two tangents from a point (external) to a circle are equal.