60 CNC Machining
• Two angles having their corresponding sides perpendicular are
equal. Thus, in Figure 3-14, Angle 1 equals Angle 2.
• A line taken from a point of tangency to the center of a circle is
perpendicular to the tangent. Thus, in Figure 3-15, Line TW is
perpendicular to Line UV.
• Two tangent lines drawn to a circle from the same exterior point
cause the corresponding segments to be equal in length. Thus, in
Figure 3-16, Segment ML equals Segment MN.
3 2
1
4 4
1
2
T
U
V
W
M
W
L N
Figure 3-13. Angle 4, an exterior angle,
equals the sum of Angles 1 and 2, which are
nonadjacent interior angles.
Figure 3-14. Angle 1 is equal to Angle 2 because their
corresponding sides are perpendicular to each other.
Figure 3-15. Line TW, developed from the
tangency point to the circle’s center, is
perpendicular to tangent Line UV.
Figure 3-16. Lines MN and ML are tangent to the
circle and share an endpoint and are, therefore, equal
in length.