Angles
Parallel lines create matching angles — spot the F, Z and C shapes.
Angle factsParallel linesAngles in polygonsUnknown anglesReasoning
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Parallel lines
Corresponding (F) equal. Alternate (Z) equal. Co-interior (C) add to 180°.
Polygon interior sum
(n − 2) × 180°.
Exterior angles
Always add to 360°. Regular: 360 ÷ n.
Worked example
Interior angle sum of a pentagon
- 1n = 5
- 2(5 − 2) × 180
- 3= 540° ✅
🧪 Play with it: Angle turner
60° Acute
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