| --- |
| source: ncert |
| topic: geometry |
| class_level: class_7 |
| chapter: ch6 |
| difficulty: beginner |
| --- |
| |
| Class 7 | Ch6: Triangle Properties |
| Angle sum property: A+B+C=180° for any triangle. |
| Exterior angle = sum of two remote interior angles (not all three). |
| Triangle inequality: sum of any two sides > third side. |
| Pythagoras: c^2=a^2+b^2 where c=hypotenuse (opposite 90°, always longest). |
| Triplets: (3,4,5),(5,12,13),(8,15,17),(7,24,25). |
| Converse: if a^2+b^2=c^2 then right-angled. |
| Median: vertex to midpoint of opposite side. 3 medians meet at centroid. |
| Altitude: perpendicular from vertex. 3 meet at orthocentre. |
| Example: A=50°,B=70°,C=60°. Exterior at C=120°=A+B=50+70 verified. |
| Sides 9,40,41: 81+1600=1681=41^2 → right triangle. |
