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3.1 Lines and Angles
Unit IC Day 1
Do Now

Parallel lines have _________ slopes.
◦ Give an example of a line that is parallel to
y = -3x + 7

Perpendicular lines have ____________
slopes.
◦ Give an example of a line that is
perpendicular to y = -3x + 7
Definitions
Two lines are parallel if they are
_____________ and do not
_____________.
 Two lines are skew if they are not
_____________ and do not
_____________.


Two planes are ____________ if they do
not intersect.
Example 1: Identifying relationships in
space

a.
b.
c.
d.
Which segment(s) in the diagram appear(s) to fit
the description?
Parallel to AB and contains D
Perpendicular to AB and contains D
Skew to AB and contains D
Name the plane(s) that contains D and appear to
be parallel to plane ABE.
Postulate 13: Parallel Postulate

If there is a line and a point not on the
line, then _____________________
through the point, parallel to the given
line.
P
l
Postulate 14: Perpendicular Postulate

If there is a line and a point not on the
line, then ___________________
through the given point, perpendicular to
the given line.
P
l
Definitions:

Transversal: a line that intersects two or more
coplanar lines at different points.

________________: occupy corresponding
positions.
◦ Examples:

_______________: lie outside the two lines,
on opposite sides of the transversal.
◦ Examples:

_______________: lie between the two lines,
on opposite sides of the transversal.
◦ Examples:

________________: lie between the two
lines, on the same side of the transversal
◦ Examples:
Ex. 2: Identifying Angle Relationships
List all of the pairs of angles that fit the
description.
a)
Corresponding
b)
Alternate exterior
c)
Alternate interior
d)
Consecutive interior
Perpendicular Construction
1.
Draw a line ℓ and a point P not on ℓ.
1.
Place the compass at point P and draw an arc
that intersects the line ℓ twice. Label the
intersections A and B.
1.
Place the compass at point A and draw an arc.
Using the same radius, place the compass at
point B and draw another arc. Label the
intersection of the arcs Q.
1.
Use a straight edge to draw PQ.
Closure

If two lines are cut by a transversal, how
many pairs of corresponding angles are
formed?