Circles Unit 9

Front

What is the area of a circle with a radius of 3 cm?

Back

Area = πr² = π(3)² = 28.27 cm² (approximately)

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2πr or Circumference = πd, where r is the radius and d is the diameter.

Front

If a circle has a diameter of 10 cm, what is its radius?

Back

Radius = Diameter / 2 = 10 cm / 2 = 5 cm.

Front

What is the relationship between the diameter and the radius of a circle?

Back

The diameter is twice the length of the radius.

Front

What is an inscribed angle in a circle?

Back

An inscribed angle is formed by two chords in a circle which have a common endpoint.

Front

If an inscribed angle intercepts an arc of 80°, what is the measure of the inscribed angle?

Back

The inscribed angle is half the measure of the intercepted arc, so it is 40°.

Front

What does it mean if a diameter is perpendicular to a chord?

Back

It means that the diameter bisects the chord and the corresponding arc.

Front

What is the measure of a central angle in a circle?

Back

A central angle is equal to the measure of the arc it intercepts.

Front

How do you find the length of an arc in a circle?

Back

Arc length = (θ/360) × 2πr, where θ is the central angle in degrees.

Front

What is the area of a sector of a circle?

Back

Area of sector = (θ/360) × πr², where θ is the central angle in degrees.