Same-Side Interior Angles

Lines AB and FC are parallel. Line BC is a transversal.

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1. Use points A, B, and C to move the lines. Observe the angle values.
2. <ABC and <FCB are same-side interior anlges. Name another pair of same-side interior angles.
3. What is always true about same-side interior angles formed when parallel lines are intersected by a transversal?
4. Prove your conjecture from question #3.

Barbara Perez, 11/7/06, Created with GeoGebra