Chapter 6 Basic Geometric Constructions 173
are measured counterclockwise from 0° hori-
zontal. For example, the entry @345 locates a
point three units from the previous point at an
angle of 45° counterclockwise in the XY plane.
1. Line AB is given, Figure 6-17A. An
inclined line is to be drawn at 60° coun-
terclockwise at Point C.
2. Enter the
Line
command and
specify Point C as the first point. When fi
prompted for the second point, enter
@660. You can also use polar tracking
and direct distance entry. This draws a
line from Point C to Point D and forms a
60° angle (Angle DCB), Figure 6-17B.
Constructing Polygons
A polygon is a geometric figure enclosed fi
with straight lines. A polygon is called a regular
polygon when all sides are equal and all interior
angles are equal. Common polygons are shown
in Figure 6-18. The procedures in the follow-
ing sections show how to construct triangles,
squares, and other common polygons.
Figure 6-16. A protractor is used to lay out angles.
A
D
35–
C
Figure 6-18. A—A polygon is a geometric fi gure enclosed with straight lines. B—A regular polygon has all sides
equal and all interior angles equal.
Right
triangle
One 90– angle
Equilateral
triangle
3 sides
Square
4 sides
Pentagon
5 sides
Hexagon
6 sides
Heptagon
7 sides
Octagon
8 sides
Isosceles
triangle
Two sides equal
Two angles equal
Scalene
triangle
No equal
sides or angles
Rectangle
Opposite sides
equal; 90– angles
Rhomboid
Opposite
sides equal
Trapezoid
Two sides
parallel
Trapezium
No sides or
angles equal
Polygons
A
Regular Polygons
B
Figure 6-17. Using polar coordinates to draw an
inclined line at a given angle. A—Line AB and
Point C are given. B—The polar coordinate @660 is
specified for the second point when drawing Line CD.
A B
C
A
C
B
60
–
6.0 units
(2,0)
(@660) D
A B