ma
Angles in Polygons
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
Free online summary and notes (ICSE Class 10 Hindi). Read it here, no PDF download needed.
About the author
Mathematics · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
Each triangle holds 180°. So the interior angles add to (n - 2) × 180°. A pentagon gives 3 triangles = 540°.
Each interior angle = (n - 2) × 180° ÷ n. A regular hexagon: 720 ÷ 6 = 120°.
This is true for every convex polygon. For a regular one, each exterior angle = 360° ÷ n.
Know one and subtract from 180° to get the other. Pick whichever route is shorter for the problem.
Hard words & meanings
| polygon | a closed flat shape made only of straight sides |
| interior angle | the angle inside the polygon at a vertex |
| exterior angle | the angle between a side and the extension of the next side |
| regular polygon | a polygon with all sides equal and all angles equal |
| convex | a polygon with every interior angle less than 180° and no dents |
| vertex | a point where two sides of a polygon meet; plural vertices |
| diagonal | a straight line joining two non-adjacent vertices |
| supplementary | two angles that add up to 180° |
Model exam answers, grammar & audio
You have read the summary. The board-ready model answers, grammar notes, one-touch audio and writing practice for this chapter are part of Lipi©.
Sign in to unlockSee it, understand it, hear it read aloud, then write the exam answer with confidence, for a fraction of a tutor cost.