1.5. Angle Measurement http://www.ck12.org
- Move the point of the compass to the horizontal side of the angle we are copying. Place the point where the
arc intersects this side. Open (or close) the “mouth” of the compass so you can draw an arc that intersects the
other side of the arc drawn in #2. Repeat this on the line we drew in #1. - Draw a line from the new vertex to the arc intersections.
To watch ananimationof this construction, see http://www.mathsisfun.com/geometry/construct-anglesame.html
Example A
Measure the three angles using a protractor.
It might be easier to measure these three angles if you separate them. With measurement, we put anmin front of the
(^6) sign to indicate measure. So,m (^6) XUY= 84 ◦,m (^6) Y U Z= 42 ◦andm (^6) XU Z= 126 ◦.
Example B
What is the measure of the angle shown below?