Drawing Aids, Continued
To use a protractor for laying off or measuring angles, follow this table:
Place the protractor along a straight line CA.
Place the O degree mark at the vertex of the desired angle.
Locate the desired angle (b) and its corresponding compliment (d).
Draw line BD.
Using four points of reference decreases the possibility of error in
Figure 2-51 illustrates the stability of a four-point reference system.
Figure 2-51. Protracting an angle using four-
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