Creating and understanding circles and their parts

This lesson will offer a hands-on opportunity to explore and construct circles. Students will develop a definition for identifying the parts of a circle such as the center, radius, diameter, chord, and circumference. Students will use compasses and rulers in constructing these parts of a circle.

A lesson plan for grades 6–7 Mathematics

By Patricia Tingen

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Related pages

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• Discovering Pi: This lesson introduces students to Pi through the discovery method of instruction. Students practice simple measuring skills to discover the relationship between the circumference and diameter of circular objects (Pi).They will be able to use this concept to find the circumference of any circle when the diameter is given.
• Measuring pots: Students will use an activity sheet or modern pottery rim sherds to compute circumference from a section of a circle and construct analogies based on their own experience about possible functions of ancient or historic ceramics.

Related topics

• Learn more about circles, compasses, diameter, mathematics, measurement, and radius.

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Learning outcomes

Students will:

• construct circles using a compass.
• draw in the following parts of a circle: center, radius, diameter, and chord.
• develop word meanings from the circle part illustrations.

Teacher planning

Time required for lesson

2 hours

Materials/resources

Teacher: overhead projector,compass, and ruler (cm.and in.)
Students: pencil, paper, compass, and ruler (cm. and in.)

Pre-activities

• Review with students objects with a circular shapes and find these shapes in the classroom.
• Review with students the proper way to construct a circle with a compass.

Activities

Session 1

(1 hour period)

1. The teacher will follow these steps on the overhead projector demonstrating for the students how to construct circles. Using compasses, have students construct different sized circles through experimentation.
2. Next, have all students construct a circle putting in the center point. Using a ruler students will draw a line segment through the center of the circle with endpoints on the circle. Identify this segment as the diameter of the circle. Label it. Measure the length of the diameter and record length in inches.
3. Next draw a line segment from the center of the circle to a point on the circle. Label this distance as the radius. Measure its length in inches. Compare the lengths of the radius and diameter and draw conclusions about their relationship (Ex.2 radii=1 diameter).
4. Last of all, draw a line segment not including the center of the circle but having endpoints on the circle. Label the segment chord. Have students repeat the above steps for drawing and labeling circles but specify the length of the radius.
5. Working in pairs, have students check their partner’s circle for accuracy. Students should write the meanings of their circle parts in their own words.

Session 2

(1 hour)

1. Orally review the meanings of circle parts (center, radius, diameter, and chord).
2. Using the overhead projector have student volunteers to label a sample circle for review.
3. Turn off overhead.
4. Ask students using a compass to construct a circle with a 5 cm. radius independently. They will also need to label the center. Using a cm. ruler they will construct the diameter, radius, and chord of the circle.
5. Randomly check student drawings.
6. Use any worksheets or textbook pages that meet the lesson’s objectives for more practice.

Assessment

• Require students to draw a specific size circle and label the circle parts.
• Use sample questions from EOG Testlets to check student understandings.
• Use any worksheets or textbook pages that meet the lesson’s objectives.

Supplemental information

Comments

Another extension of this lesson could be allowing students to create circle designs and then color them for various geometrical effects.