501 Geometry Questions

Skew linesare noncoplanar lines that never intersect. They exist in two
different planes, and travel dissimilar paths that will never cross. This is
hard to draw, because it is hard to represent different planes in a two-
dimensional drawing, but lines aand bbelow are skew. There is no sym-
bol to represent skew lines.

Intersecting Lines

When two lines are not parallel or skew, they will intersect. When two lines
intersect, the point of the intersection is a point that exists on both lines—
it is the only point that the lines have in common. Two intersecting lines
create four angles. In Figure 3.3 below, line aand line bintersect at point
c, creating the four different angles, d, e, f, and g. When two lines inter-
sect, the sum of the four angles they create is 360°. You can tell this is true
by looking at line b: angles eand fmake a straight angle aboveline b, so they
add to 180°, and angles dand gmake a straight angle belowline b, so they
also add to 180°. Therefore, the four angles together add to 360°.

Now that you understand how intersecting lines create angles, it is time
to learn about the special relationships that can exist between angles. When
the sum of the measurement of any two angles equals 180°, the angles are
called supplementary angles.

c

b

a

d

f

g

e

Figure 3.3

Figure 3.2

Skew lines

a and b

a

b

501 Geometry Questions