In many geometry courses, you will be expected to divide a circle equally into thirds. Since a circle is 360 degrees, you might know that a circle can be split up into three equal, 120 degree parts. If you have a compass, protractor and ruler, it is easy to measure and draw three equal portions to satisfy this assignment.

- Skill level:
- Easy

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### Things you need

- Paper
- Pencil
- Compass
- Ruler

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## Instructions

- 1
Draw a straight line segment (also called a chord) using your ruler inside your circle, so that each end touches an edge of the circle.

- 2
Label this line segment "AB."

- 3
Draw two circles of equal size using your compass, one with a centre on "A," and the other with the centre on "B." Make the radii of these circles at least 1/2 of the length of "AB," so that your two new circles intersect.

- 4
Draw a line segment "CD" across the intersection of the two new circles using your ruler, extending it to the edge of your original circle.

- 5
Erase the two new circles, but leave the line segments.

- 6
Draw two new circles of equal size using your compass, one with a centre on "C," and the other with the centre on "D." Make the radii of these circles at least 1/2 of the length of "CD" so that your two new circles intersect.

- 7
Draw another line segment using your ruler across the intersection of the two new circles. You can call this line segment "EF."

- 8
Notice where the line segment "EF" bisects the line segment "CD." This is the centre of your circle.

- 9
Place a protractor so that the base runs along either the "EF" or "CD" line segment and the origin is on the centre of your circle.

- 10
Measure a 120 degree angle by locating the zero degree and 120 degree points on the protractor and marking these points on your circle.

- 11
Draw lines from the centre of the circle through the marks you made up to the edge of the circle.

- 12
Place your protractor so that the origin is on the centre of your circle and the base runs along one of the new lines you just made.

- 13
Measure a second 120 degree angle by locating the zero degree and 120 degree points on the protractor and marking these points on your circle.

- 14
Draw lines from the centre of the circle through the marks you made up to the edge of the circle. Now the circle is sectioned into three equal parts.