Circles: Parts, C & A, Central Angles

Front

What is the formula for the circumference of a circle?

Back

C = 2πr, where C is the circumference and r is the radius.

Front

What is the formula for the area of a circle?

Back

A = πr², where A is the area and r is the radius.

Front

What is a central angle in a circle?

Back

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

Front

What is the relationship between the measure of an arc and the central angle?

Back

The measure of an arc is equal to the measure of the central angle that subtends it.

Front

Define a chord in a circle.

Back

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

Front

What is a diameter?

Back

A diameter is a chord that passes through the center of the circle, and it is the longest chord.

Front

What is a radius?

Back

A radius is a line segment from the center of the circle to any point on the circle.

Front

What is a tangent to a circle?

Back

A tangent is a line that touches the circle at exactly one point.

Front

What is a point of tangency?

Back

A point of tangency is the point where a tangent touches the circle.

Front

What is the relationship between a radius and a tangent?

Back

A radius drawn to the point of tangency is perpendicular to the tangent line.