A simple extension of the Inscribed Angle Theorem shows that the measure of the angle of intersecting chords in a circle is equal to half the sum of the measure of the two arcs that the angle and its … [Read more...] about Angles of Intersecting Chords

# Chords

A chord is a straight line connecting two points on the circle.

The diameter is a special chord, which passed through the center of the circle, and its length is 2*r. It is the longest possible chord in the circle.

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*Now that we've explained the basic concept of chords in geometry, let's scroll down to work on specific geometry problems relating to this topic.*

## Concentric Circles Intersected by a Secant

Two circles that have the same center point are called concentric circles. A secant is a line that interest a circle (or any other curved line) at two or more point. We will now show that a secant … [Read more...] about Concentric Circles Intersected by a Secant

## Finding the Length of a Common Chord

If we know the radii of two intersecting circles, and how far apart their centers are, we can calculate the length of the common chord. Problem Circles O and Q intersect at points A and B. The … [Read more...] about Finding the Length of a Common Chord

## Common Chord of Two Circles

In today's lesson, we will show that a line connecting the centers of two intersecting circles is a perpendicular bisector of the common chord of the two circles, connecting the intersection … [Read more...] about Common Chord of Two Circles

## The Tangent-Chord Theorem

The Tangent-Chord Theorem states that the angle formed between a chord and a tangent line to a circle is equal to the inscribed angle on the other side of the chord: ∠BAD ≅ … [Read more...] about The Tangent-Chord Theorem

## Intersecting Secants Theorem

In today's lesson, we will present a detailed, step-by-step proof of the Intersecting Secants Theorem, using properties of similar triangles. This is a fairly simple proof, so today's lesson will be … [Read more...] about Intersecting Secants Theorem

## Congruent Chords are Equidistant from the Center

Chords that have an equal length are called congruent chords. An interesting property of such chords is that regardless of their position in the circle, they are all an equal distance from the … [Read more...] about Congruent Chords are Equidistant from the Center

## A Diameter that Bisects Two Chords

In today's geometry lesson, we will prove that if a diameter bisects two chords in a circle, the two chords are parallel to each other. We can do this this three ways, relying on the properties of … [Read more...] about A Diameter that Bisects Two Chords

## A Diameter Perpendicular to a Chord

We've shown that a diameter that bisects a chord is perpendicular to that chord. Here, we will prove the converse theorem. Problem In circle O, the diameter AB is perpendicular to a chord CD. … [Read more...] about A Diameter Perpendicular to a Chord

## A Diameter Bisecting a Chord

There are several theorems related to chords and radii or diameters that connect to them. In today's lesson, we will first prove that a diameter that bisects a chord is perpendicular to that chord and … [Read more...] about A Diameter Bisecting a Chord