Drawing Aids, ContinuedProtractorsTo measure and lay off angles from the horizontal without triangles, use aprotractor. A protractor maybe circular or semicircular. Circularprotractors are labeled in quadrants from 0 to 90 degrees or double numberedfrom 0 to 360 degrees. Semicircular protractors are double numbered from 0to 180 degrees. Graduations in one-half degree increments allow accurateangle protraction.Figure 2-50 shows a circular and semicircular protractor.Figure 2-50. —Protractors.Continued on next page2-42
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