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How Are Tangent, Secant and Chord of a Circle Related?

Let’s take a look at different types of lines and line segments: Tangents, secants, and chords. These types of lines are often found within areas such as geometry, construction, equations and functions. This is a topic that will come up everywhere in the years to come, so let’s get you ready for it!


A line that intersects a circle or an arc at just one point, is a tangent. In everyday speech, you have probably heard the saying that someone “went off on a tangent.” This means that s/he went off in a different direction on the edge of the main subject that was being discussed.

Secant and Chord

A secant is a line that intersects a circle or arc at two points. The part of the secant that is inside the circle or arc is a chord.

The figure below shows a circle and all the different lines that you need to know. Notice that the chord lies on the inside of the circle, and that the diameter is the longest chord in the circle.

Furthermore, you need to know that the radius is equal to half the diameter. This is a relationship that you will use very often.

Circle with chord, secant, diameter, radius and tanget

Circle with chord, secant, diameter, radius and tanget

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