1. Pairs of Lines Application of Slope
G.3b
Pairs of Lines
Application of Slope
G.3b Application of Slope

2. G.3b Application of Slope
Parallel Lines
Parallel lines are coplanar lines that do not intersect.
Arrows are used to indicate that lines are parallel.
The symbol used for parallel lines is ||.
In the above figure, the arrows show that line AB is parallel to line CD.
With symbols we denote,
G.3b Application of Slope

3. G.3b Application of Slope
Parallel Planes
All planes are either parallel or intersecting. Parallel planes are two planes that do not intersect.
Ex: Plane ABCD and Plane EFGH
G.3b Application of Slope

4. G.3b Application of Slope
PERPENDICULAR LINES
Perpendicular lines are lines that intersect to form a right angle.
The symbol used for perpendicular lines is  .
4 right angles are formed. m n
In this figure line m is perpendicular to line n.
With symbols we denote, m  n
G.3b Application of Slope

5. Lesson 2-3: Pairs of Lines
OBLIQUE LINES
Oblique lines are lines that intersect, but do NOT form a right angle.
m  n 
Lesson 2-3: Pairs of Lines

6. Lesson 2-3: Pairs of Lines
Skew Lines
Two lines are skew if they do not intersect and are not in the same plane (not coplanar).
Ex:
Lesson 2-3: Pairs of Lines

7. G.3b Application of Slope
Examples:
Name all segments that are parallel to
Name all segments that intersect
Name all segments that are skew to
Name all planes that are parallel to plane ABC.
Answers:
Segments BC, FG, & EH.
Segments DH, DC, AE & AB.
Segments CG, BF, FE, & GH.
Plane FGH.
G.3b Application of Slope

8. Lesson 2-3: Pairs of Lines
Slope
The slope of the non vertical line through the points and is
m =
The slope of a vertical line is not defined.
The slope of a horizontal line is zero.
Lesson 2-3: Pairs of Lines

9. Two lines are parallel if and only if they have equal slopes.
Ex: The line y=3x+2 is parallel to the line y=3x-4
Two lines are perpendicular if and only if the product of their slopes is -1 (reciprocals and opposite signs).
Ex:
The line 𝑦= 2 3 𝑥+5 is perpendicular to the line 𝑦=− 3 2 𝑥+1
G.3b Application of Slope

10. G.3b Application of Slope
Examples
Any line parallel to a line with slope has slope _____.
Any line perpendicular to a line with slope has slope ___.
Any line parallel to a line with slope 0 has slope _____.
Any line perpendicular to a line with undefined slope has slope.
Any line parallel to a line with slope 2 has slope _____.
Zero Slope 2
G.3b Application of Slope