Polygonal Construction, Continued
Angles
The most convenient method of laying out an angle is by using a triangle or a
protractor. When absolute accuracy is important, use the tangent, sine, or
chord method. A table of trigonometric tables listing tangent, sine, and
chord values is located in the back of this book.
TANGENT METHOD: The tangent method of angle construction is a
trigonometric function of an acute angle to find the ratio of the length of the
side opposing the angle to the length of the side adjacent to the angle. In
figure 2-34, the tangent of angle
is y/x, and y=x tan
. To construct the
angle, assign a simple value to x, in this case 10. The larger the number, the
more accurate the construction. Find the tangent of angle
in a table of
natural tangents, multiply by 10 and set off y = 10 tan
.
Figure 2-34 is an angle constructed by the tangent method.
Figure 2-34.—The tangent method of angle construction.
Continued on next page
2-35
