Lesson 1: Angles - Bisecting Angles with a Protractor and Ruler

   Constructing Knowledge

To bisect an angle is to split that angle into two equal parts. Two methods for bisecting angles will be introduced in this course. The first method uses a protractor and a ruler, using the following steps.

Step 1: Measure the given angle with a protractor.

Step 2: Divide the measured angle by 2 to get the bisected angle measure.

Step 3: Lay the protractor on one of the angle arms so that the origin lines up with the vertex of the angle. Measure the number of degrees for the bisected angle, and mark the bisected angle arm point.

Step 4: Connect the marked bisected angle arm point to the vertex with a ruler.

Step 5: Check the bisected angle by measuring with a protractor.

   Multimedia

The first 90 seconds of this video describes bisecting an angle with a protractor.


EXAMPLE

Bisect the angle.



Solution


Step 1: Measure the given angle with a protractor.



The angle measures 55°.

Step 2: Divide the measured angle by 2 to get the bisected angle measure.

55° ÷ 2 = 27.5°

Step 3: Lay the protractor on one of the angle arms so that the origin lines up with the vertex of the angle. Measure the number of degrees for the bisected angle, and mark the bisected angle arm point.



Step 4: Connect the marked bisected angle arm point to the vertex with a ruler.



The angle is now bisected into angles of 27.5°.

Step 5: Check the bisected angle by measuring with a protractor.




Now, it is your turn! Complete the questions in your Chapter 6, Lesson 1 Practice Makes Perfect that refer to Bisecting Angles with a Protractor and Ruler.



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