2.2 Central Angles and Arcs
Need:
Different colored pens/pencils, markers
Pencil, pencil
Highlighter
Scissors, glue, ruler
A square with sides lengths 1 inch is inside a circle (see picture below). Calculate
the diameter of the circle.
Central Angles
The angle subtended at the center of a circle by two
given points on the circle.
http://www.mathopenref.com/circlecentral.html
Ex. 1
Find the value of x
You Try:
Find the value of x
Minor Arc
Arc that measures less than 180°
Semicircle
Major Arc
Arc that measures greater than 180°
http://www.mathopenref.com/arc.html
In a circle graph, the central angles divide a circle into wedges to represent data,
often expressed as a percent. The size of the angle is proportional to the percent.
How many total students in class right now? _________
What sport do you prefer to watch?
• Soccer ___
• Football ___
• Baseball ___
• Basketball ___
•
•
•
•
Make a bar graph of the information
Cut out each bar (each individual box)
Put the bars in a circle (as best as possible)
What part of the circles do the bar represent? How does this
relate to the central angle?
http://www.shodor.org/interactivate/activities/CircleGraph/?version=1
What’s the difference in Arc Measure and Arc Length???
http://www.mathopenref.com/arclength.html
Assignment:
Geometry Textbook
Page 696 # 12- 41