1. How do we determine if lines are parallel? 2. We can use Geogebra to help us further understand this concept. Using the slope tool, click on [b]line a[/b] and do the same with [b]line b[/b]. Notice, that the slopes are not the same. Using the cursor move points A, B, C, and D until the slopes are equal. 3. Now construct your own set of parallel lines. Use the built in tools to find the slopes are equal, then calculate the slope using an appropriate formula.