Measuring an angle using a protractor

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See also the animated version.

Begin with two lines that intersect at Q. We plan to measure angles JQM and LQK and verify the angles are the same.
Step 1 Place the protractor so that the origin (small hole) is over the point Q.
Step 2 Rotate the protractor so that the base line is exactly along the line JK.
Step 3 Using the inner scale, read the angle over the line LM. It should read 34 degrees.
This shows that the angle LQK has a measure of 34°.
Step 4 Now, rotate the protractor so that its base line is along the line LM
Step 5 Using the outer scale, read the angle over the line JK. It should read 34 degrees,
showing that the angle JQM also has a measure of 34°.
Step 6 Done. By measuring these two angles, you have verified that vertical angles are congruent.

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