# G.GCO.8 Alternate Interior Angles: Quick Investigation

- Author:
- Dan Dale, Tim Brzezinski

- Topic:
- Angles, Straight Lines

## 1.

Use the **Slope** tool to measure the slopes of the two lines *g* and *i*. Then, tamper with the **gray slider**. What do you notice about the slopes of these lines?

## 2.

What does your observation from (1) tell you about lines (g) and (i)?

## 3.

If you haven't done so yet, drag the **orange point** along transversal *n* as far as it will go. **What geometric transformation is taking place?**

## 4.

Drag the next **orange point** that appears. What geometric transformation is taking place here?

## 5.

Did any of these transformations change the **size of the angle at all**? If so, how? If not, why not?

## 6.

If a transversal (in this case, *n*) intersects 2 lines that have the property that you wrote in response to (2) above, what can you conclude about a pair of **blue alternate interior angles **that were formed?