Tangents and Secants
In a plane, a line is tangent to the circle if and only if it intersects a circle in exactly one point.
A secant of a circle is a line that intersects a circle in two points.
Postulate: At a given point on a given circle, one and only one line can be drawn that is tangent to the circle.
Tangent Theorem: In a plane, if a line is tangent to a circle, then it is perpendicular to the radius drawn to the point of tangency.
Converse of Tangent Theorem: In a plane, if a line is perpendicular to a radius of a circle at the endpoint on the circle, then the line is tangent to the circle.
A common tangent is a line that is tangent to each of two circles.
Find out more about tangents and secants below.
Practice: Identify and apply properties of tangents and secants to circles in the following exercises.