Alternate Interior Angles -- When are they congruent?

1. Are the angles congruent? 2. Drag the point to see what changes. 3. You can use checkboxes Compare Angles and Compare Lines to get more information. 4. Play The Congruent Game! What's your top score? 5. Make a conjecture... when are the angles congruent? 6. Are there other conjectures we could make about other lines or other angles in this picture?
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