Lesson 1: 9-1: Circles and Circumference

1. What is the center of a circle?
2. What is the difference between a diameter and a radius?
3. How do you find the circumference of a circle?

Circle
Center
Radius
Chord
Diameter
Concentric Circles
Circumference
Pi
Inscribed
Circumscribed

G.CO.1
Know precise definitions of angle, circle, perpendicular line, parallel line, and line segment, based on the undefined notions of point, line, distance along a line, and distance around a circular arc.
G.C.1
Identify and describe relationships among inscribed angles, radii, and chords.

A circle is the locus of all points in a plane equidistant from a given point. Any segment with endpoints on the circle is a chord. A chord that contains the center of the circle is a diameter. Any segment with endpoints that are the center and a point on the circle is a radius. For circumference C and a diameter d or a radius r, C=pi*d or C=2*pi*r.

The maxAir ride speeds back and forth and rotates counterclockwise. At times, the riders are upside down 140 feet above the ground experiencing "airtime" - a feeling of weightlessness. The ride's width - or diameter - is 44 feet. You can find the distance that a rider travels in on rotation by using this measure.

When working with formulas involving circles, be careful to check if information is given about the radius or the diameter.

Students approaching grade level can be given practice problems in small groups to work with other students or directly with the teacher.
Students beyond grade level can make deeper connections by finding the radius or the diameter of a circle given the circumference.

Formative Assessment

Textbook in class

Access online textbook and resources through class link.