Polygonal Construction, Continued
Triangles
(Continued)
You may also use a protractor to construct triangles.
To use a protractor or semicircular protractor to construct an equilateral
triangle, use this table:
Step
Action
1
With a straightedge, draw a line (AB) at any convenient length and
a perpendicular line at the center.
2
Place the center of the protractor (usually marked 0) at A, align the
protractor with the line AB.
3
Locate the 60° increment on the protractor and lightly mark your
paper. If using a full circular protractor, you can increase accuracy
by also locating and marking the opposing angle. This allows you
to use the four-point reference system (DM Volume 1, chapter 2).
4
Move the protractor to B on line AB. Locate and mark the drawing
at the 60º increment. Also mark the opposing angle , if possible.
5
Draw straight lines through the marked increments terminating at
the perpendicular line. These lines should intersect forming an
equilateral triangle.
Figure 2-38 shows an equilateral triangle constructed by using a protractor.
Figure 2-38.—Constructing an
equilateral triangle with a protractor.
Continued on next page
2-39
