Circle

One point allows infinitely many circles

One point allows infinitely many circles. Two distinct points also allow infinitely many circles, and their centres lie on the perpendicular bisector

A tangent touches a circle at

A tangent touches a circle at exactly one point, called the point of contact. A secant cuts a circle at two points. A line with no common point with a

A tangent at any point

A tangent at any point of a circle is perpendicular to the radius at the point of contact. Also, a line perpendicular to a radius at its point on the

Tangent segments drawn from an external

Tangent segments drawn from an external point to a circle are congruent. If two tangents are drawn from the same outside point, their lengths are equa

If two circles touch

If two circles touch, their point of contact lies on the line joining their centres. For externally touching circles, the distance between centres equ