Explore It! Arc and Angle Measure!

Author:Elisabeth Hipke, Suzanne Gibbons, Emily_Gabriel1

In this activity you will discover relationships in circles that involve arc and angle measures.

How do you measure arcs?

Central angles have a vertex at the center of the circle. An intercepted arc is a portion of the circumference of a circle encased by two line segments meetings at a vertex. Arcs can be measured in degrees. Drag points A, B, and C. as directed to determine the relationship between the degree of an arc and the central angle that creates the arc.

Move point B around for a bit. What happens to the circle when you move B?

Move point B around to change the size of the circle. Where is point B located?

Select all that apply

A
on the circle's edge
B
at the center of the circle
C
randomly in the circle
D
outside the circle

Check my answer (3)

Click on point C. Move it to the right and left along the circle. *Do NOT move it past A in either direction*

What is the relationship between the central angle and the intercepted arc CA?

Move point D along the circle to the right and left. *Do NOT move D past point C or point A*

What happened to arc DC as you moved point D?

What happened to arc CA as you moved point D?

What is the relationship between arcs DC, CA and DA?

This time move point C back and forth between points D and A. What happens to arc DC?

This time move point C back and forth between points D and A. What happens to arc CA?

What is the relationship between arcs DC, CA and DA?

This time move point A back and forth. *Do NOT pass points C or D* What happens to arc DC?

What is the relationship between arcs DC, CA and DA?

Explore It! Arc and Angle Measure!

How do you measure arcs?

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