CK-12 Geometry-Concepts

http://www.ck12.org Chapter 1. Basics of Geometry

This angle is not lined up with 0◦, so use subtraction to find its measure. It does not matter which scale you use.

Using the inner scale,| 140 − 25 |= 125 ◦

Using the outer scale,| 165 − 40 |= 125 ◦

Example C

What ism^6 QRTin the diagram below?

Using the Angle Addition Postulate,m^6 QRT= 15 ◦+ 30 ◦= 45 ◦.

Example D

Draw a 135◦angle.

Following the steps from above, your angle should look like this:

Watch this video for help with the Examples above.

MEDIA

Click image to the left for use the URL below.

URL: http://www.ck12.org/flx/render/embeddedobject/52599

CK-12 Foundation: Chapter1MeasuringAnglesB

Vocabulary

Aprotractoris a measuring device that measures how “open” an angle is. Angles are measured indegrees, and
labeled with a◦symbol. Acompassis a tool used to draw circles and arcs.