Circles and Circumference

Vocabulary A ________is a plane figure that consists

of a set of points that are equidistant from a given point called the center.

The ____________of a circle is the distance around it.

circle

circumference

Identifying the Parts of a Circle

A __________is a line segment that connects the outside of the circle to its center.

radius

A ______________is a line segment with both endpoints on the circle that passes through the center.

diameter

A _________is a line segment whose endpoints are on the circle.

Chords do not have to pass through the center of the circle. However, if a chord does pass through the center, it is also considered a _______________.

chord

A diameter is a line segment with both endpoints on the circle that passes through the center.

A chord is a line segment whose endpoints are on the circle.

Chords do not have to pass through the center of the circle. However, if a chord does pass through the center, it is also ______________________.Considered a diameter

Numerical Relationships A radius is exactly ________of a diameter. Therefore a diameter is _______a radius.

5.5 cm

If the radius is 5.5 cm, then the diameter is ___________ cm.11

Numerical Relationships A radius is exactly one-half of a diameter. Therefore a diameter is twice a radius.

5.5 cm

If the radius is 5.5 cm, then the diameter is ___________ cm.11

Circumference Remember, _____________is the distance

around the circle. If you divide a circle’s circumference by its

diameter, you ______________get the same irrational number – pi (symbol: ¶ )

This is true of every circle. We estimate pi to be 3.14 or the

fraction 22/7.

Circumference Remember, circumference is the distance

around the circle. If you divide a circle’s circumference by its

diameter, you always get the same irrational number – pi (symbol: ¶ )

This is true of every circle. We estimate pi to be 3.14 or the

fraction 22/7.