Download 3-1 Lines and Angles

3-1 Lines and Angles
Parallel and Skew
• Parallel lines are coplanar lines
that do not intersect.
– The symbol  means “is parallel to”.
• Skew lines are noncoplanar; they
are not parallel and do not intersect.
• Parallel planes are planes that do not
intersect.
– A line and a plane can be parallel; segments and
rays can be parallel or skew.
Identifying Nonintersecting Lines and
Planes
Which segments are parallel
to AB?
Which segments are skew to
CD?
What are two pairs of parallel planes?
What are two segments parallel to plane BCGF?
Why are FE and CD not skew?
Angles Pairs Formed by Transversals
A transversal is a line that intersects two or
more coplanar lines at different points (line t).
Two angles are corresponding angles if they
occupy corresponding positions (1 and 5,
3 and 7, 2 and 6, 4 and 8).
1 2
3 4
5 6
7 8
t
Two angles are alternate exterior angles if they lie outside the two lines
on opposite sides of the transversal (1 and 8, 2 and 7).
Two angles are alternate interior angles if they lie between the two lines
on opposite sides of the transversal (3 and 6, 4 and 5).
Two angles are consecutive (or same side) interior angles if they lie
between the two lines on the same side of the transversal (3 and 5, 4
and 6).
Identifying an Angle Pair
Identify all pairs of angles with the following
relationships:
– Alternate interior
– Same-side interior
– Corresponding
– Alternate exterior