Circles: Arcs, Angles, and Vocabulary

Front

What is a circle?

Back

A circle is a set of points in a plane that are equidistant from a fixed point called the center.

Front

What is the radius of a circle?

Back

The radius is the distance from the center of the circle to any point on its circumference.

Front

What is the diameter of a circle?

Back

The diameter is twice the length of the radius and is the longest distance across the circle, passing through the center.

Front

What is an arc in a circle?

Back

An arc is a portion of the circumference of a circle.

Front

What is a central angle?

Back

A central angle is an angle whose vertex is at the center of the circle and whose sides intersect the circle.

Front

How do you find the measure of an arc?

Back

The measure of an arc is equal to the measure of its central angle.

Front

What is a secant line?

Back

A secant line is a line that intersects a circle at two points.

Front

What is the relationship between the angles formed by two intersecting chords?

Back

The measure of the angle formed by two intersecting chords is equal to half the sum of the measures of the arcs intercepted by the angle.

Front

What is the formula for the circumference of a circle?

Back

The circumference (C) of a circle is given by the formula C = 2πr, where r is the radius.

Front

What is the formula for the area of a circle?

Back

The area (A) of a circle is given by the formula A = πr², where r is the radius.