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GeoGebraGeoGebra Classroom

Alternate Interior Angles: Quick Investigation

The directions for this activity can be found below the applet.


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?


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


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?


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


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


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?

Quick Demo. (BGM: Andy Hunter)