Chapter 6 Basic Geometric Constructions 185
Figure 6-33. Constructing an octagon when the
distance across the fl ats is given. A compass and a
45° triangle are used.
Distance
across flats
A B
Distance
across flats
Construct an
Octagon with the
Distance across the Corners
Given Using the Circle
Method
1. With a compass, draw a circle equal
in diameter to the distance across the
corners, Figure 6-34A.
2. With a T-square and a 45° triangle, lay
off 45° diagonals with the horizontal and
vertical diameters (centerlines).
3. With the triangle, draw the eight sides
between the points where the diagonals
intersect the circle, Figure 6-34B.
Figure 6-34. Constructing an octagon when the
distance across the corners is given. The sides are
constructed after drawing a circle and 45° diagonals.
A B
Distance
across corners
45–
Distance
across corners
45–
Figure 6-35. If the distance across the fl ats is known, an octagon can be constructed using the square method.
A compass, straightedge, and 45° triangle are used.
A
Distance
across flats
Distance
across flats
B C
Construct an
Octagon with the
Distance across the Flats
Given Using the Square
Method
1. Draw a square with the sides equal to
the given distance across the flats, fl
Figure 6-35A.
2. Draw diagonals at 45°. With a radius equal
to one-half the diagonal and using the
corners of the square as vertices, scribe
arcs using a compass, Figure 6-35B.
3. With a 45° triangle and a T-square,
draw the eight sides by connecting the
points of intersection. This completes the
required octagon, Figure 6-35C.