Beyond Rankers Academy
Building Minds, Not Just Rankers
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Beyond Rankers Academy
Building Minds, Not Just Rankers
Main site →
Angles have exact names for exact ranges of degrees. Triangles and quadrilaterals sort into families by their sides and angles. And solids have their own count of faces, edges and corners.
An angle is measured in degrees with a protractor. Its size decides its name.
| Angle | Range |
|---|---|
| Acute | between 0° and 90° |
| Right | exactly 90° |
| Obtuse | between 90° and 180° |
| Straight | exactly 180° |
| Reflex | between 180° and 360° |
| Complete angle | exactly 360° (a full turn) |
A triangle can be classified by its SIDES, or by its ANGLES — and its 3 angles always add to 180°.
By sides
Equilateral (3 equal) · Isosceles (2 equal) · Scalene (none equal)
By angles
Acute-angled (all < 90°) · Right-angled (one = 90°) · Obtuse-angled (one > 90°)
A quadrilateral's 4 angles always add to 360°. A solid has faces, edges and vertices in fixed numbers.
12 IMO-style questions on angles, triangles, quadrilaterals and solids. 🍀