# GARIS TEGAK LURUS

- Author:
- Mardia Hayati, GeoGebra Team

What does it mean for lines to be perpendicular (by definition)?

## Reposition line f below so that its slope becomes 4/3. Then slowly slide the slider you see all the way to the right.

If the **slope of line f**

*=*and line

*is perpendicular to line*

**g***f*,

**what is the slope of line**? If you forget how to find the slope of a line by inspection, click here for a quick reminder.

*g*## Reposition line f below so that its slope becomes -2/5. Then slowly slide the slider you see all the way to the right.

If the **slope of line f **= and line

*is perpendicular to line*

**g***f*,

**what is the slope of line**? If you forget how to find the slope of a line by inspection, click here for a quick reminder.

*g*Notice anything interesting between slopes of perpendicular lines drawn in the coordinate plane? If so, please describe.