A triangle is the simplest closed shape — just 3 corners (vertices) and 3 sides. Let's meet its rules and its different types!
📛Naming: A triangle with corners A, B, C is written △ABC. The corners can be named in any order.
📏Triangle Inequality: A triangle can only be built if EVERY side is shorter than the sum of the other two sides. If not, the sides just won't meet up!
📐Angle Sum Property: The three angles inside ANY triangle always add up to exactly 180°. Always. No exceptions!
🔻By sides: Equilateral = all 3 sides equal. Isosceles = 2 sides equal. Scalene = all 3 sides different.
📊By angles: Acute = all angles under 90°. Right = one angle exactly 90°. Obtuse = one angle over 90°.
📉Altitude: A straight, perpendicular "height line" from a corner down to the opposite side.
Try thisCan sides 3 cm, 4 cm, 8 cm form a triangle? Check: is 8 < 3+4? No, 8 > 7. So no triangle is possible. But 3 cm, 4 cm, 5 cm works because 5 < 3+4 (and every other pair checks out too)!
Start the challenge ↓