Parallel Lines

Slope and Parallelism

​Why is this relevant?

Geometry is the study of physical space (both 2 dimensional and 3 dimensional). We can use coordinate geometry to help us map and plan in 2D before bringing plans to life in 3D

Open Ended

In what real life scenarios would it be important to create something in 2 dimensions before constructing in 3 dimensions?

Two line segments AB and CD are shown graphed to the left. Determine the slope of both of these lines graphically. Recall that slope is the ratio of the rise to the run as we move from left to right.

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​Exercise 1

Fill in the Blanks

The rise (change in y) of AB is

Fill in the Blanks

The run (Change in x) of AB is

Multiple Choice

The slope (Change in y / Change in x) is

• -1/2

• 2

• -2

• 1/2

Poll

Before finding the slope of CD should it be positive or negative?

• Positive

• Negative

Open Ended

What is the slope of CD?

Draw

How can we show on the graph the slope of AB?

If (x1, y1) and (x2,y2) represent the endpoints of a line segments (or any two points on a line), then

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Slope Formula

Fill in the Blanks

Considering Exercise 2A what number can we substitute in for y1?

Fill in the Blanks

If y1 is 10 then x1 is

Fill in the Blanks

The slope of AB is

Draw

Show the substitution to calculate the slope of CD.

Multiple Choice

What is the slope of EF?

• Error

• 1/2

• 0

• 2

Fill in the Blanks

Name the Parallel line pairs.

Draw

Find the slopes of all 4 lines on the graph provided.

Fill in the Blanks

What do you notice about the lines that are parallel?

Two non-vertical lines will be parallel if and only if they have slopes that are equal.

Fill in the Blanks

What is the slope of AB?

Fill in the Blanks

What is the slope of CD?

Open Ended

Are the lines AB and CD parallel? Why?

Open Ended

Are AC and BD Parallel? How do you know?