Circles: Vocabulary and Formulas

Front

What is the definition of a radius in a circle?

Back

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

Front

What is the formula for the circumference of a circle?

Back

The circumference (C) is calculated using the formula: C = 2πr, where r is the radius.

Front

What is the diameter of a circle?

Back

The diameter is the distance across the circle through its center, equal to twice the radius.

Front

What is the relationship between radius and diameter?

Back

The diameter is twice the length of the radius: d = 2r.

Front

What is a chord in a circle?

Back

A chord is a line segment with both endpoints on the circle.

Front

What is an inscribed angle?

Back

An inscribed angle is formed by two chords in a circle which share an endpoint.

Front

How do you find the radius if you know the diameter?

Back

To find the radius, divide the diameter by 2: r = d/2.

Front

What is the area of a circle?

Back

The area (A) is calculated using the formula: A = πr², where r is the radius.

Front

What is the circumference of a circle with a radius of 10?

Back

Using the formula C = 2πr, the circumference is C = 2π(10) = 20π.

Front

If the radius of a circle is 6 cm, what is the diameter?

Back

The diameter is d = 2r = 2(6) = 12 cm.