# Slopes of Parallel and Perpendicular Lines - Discovery & Assessment: Quick Demo

- Author:
- Tim Brzezinski

## Note the slope of line j = 3/5. Move the sliders (top left) to change the slope of line k SO BOTH LINES LIE PERFECTLY ON TOP OF EACH OTHER.

Now move the LARGE WHITE POINT you see below where it currently is. What word would you use to describe the lines now?

What do you notice about the slopes of both of these lines?

## Note the slope of line j = 3/5. Change the slope of line k so that LINES J and K become PERPENDICULAR.

How do you know your two lines are perpendicular? Briefly explain.

What do you notice about these two slopes above? How do they compare?

## We can also use GeoGebra to assess students' knowledge of what they discover. Immediate feedback and conceptual scaffolding provided.

## TEACHERS:

For links to 2 full engaging lessons where students explore slopes of parallel lines and perpendicular lines,

**click here**.