1. 3.6 Parallel Lines in the Coordinate Plane
Geometry
3.6 Parallel Lines in the Coordinate Plane

2. Geometry 3.6 Parallel Lines in the Coordinate Plane
Goals
Find the slope of lines on the coordinate plane.
Determine if two lines are parallel.
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane

3. Geometry 3.6 Parallel Lines in the Coordinate Plane
Review: Slope
Slope =
Rise
Run
Run = 6
(3, 3)
Rise =4
(-3, -1)
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane

4. Geometry 3.6 Parallel Lines in the Coordinate Plane
Reminder
Lines with a positive slope rise to the right.
Lines with a negative slope rise to the left.
Lines with zero slope are horizontal.
Lines with no slope are vertical.
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane

5. Geometry 3.6 Parallel Lines in the Coordinate Plane
Another Example
Slope =
Rise
Run
Run = -3
(-1, 3)
Rise =3
(2, 0)
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane

6. We can also use the formula.
Given two points
and
The slope is
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane

7. Geometry 3.6 Parallel Lines in the Coordinate Plane
Example
Find the slope of the line that passes through (9, 12) and (6, -3).
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane

8. Geometry 3.6 Parallel Lines in the Coordinate Plane
Postulate 17
Parallel lines have the same slope.
We write:
m1 = m2
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane

9. Geometry 3.6 Parallel Lines in the Coordinate Plane
Summary
Slope measures the steepness of a line.
Slope is the Rise/Run.
Parallel lines have the same slope.
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane

10. Geometry 3.6 Parallel Lines in the Coordinate Plane
Homework
February 21, 2019
Geometry 3.6 Parallel Lines in the Coordinate Plane