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Measuring an angle using a protractor

This is the step-by-step, printable version. If you PRINT this page, any ads will not be printed.

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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Other constructions pages on this site

Lines

Angles

Triangles

Right triangles

Triangle Centers

Circles, Arcs and Ellipses

Polygons

Non-Euclidean constructions