SAT Math: Find angle measures formed by parallel lines and a transversal (alternate interior, corresponding, co-interior)
26+ practice questions in Praczo
The concept, explained
- 1
When a transversal crosses two parallel lines, it creates 8 angles with special relationships.
- 2
Corresponding angles (same position at each intersection) are equal. Alternate interior angles (inside, opposite sides of transversal) are equal. Alternate exterior angles are equal.
- 3
Co-interior (same-side interior) angles are supplementary: they sum to 180°.
- 4
Vertical angles (opposite at a single intersection) are always equal, whether or not the lines are parallel.
- ✗ Confusing corresponding and alternate interior angles. Both are equal, but they're in different positions.
- ✗ Treating same-side interior angles as equal instead of supplementary.
SAT-style practice
Two parallel lines are cut by a transversal. One of the angles measures 65°. What is the measure of the alternate interior angle?
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