Rectangles — A Complete Guide for Grade 8
📐 Formal Definition
A rectangle is a quadrilateral (4-sided polygon) in which all four interior angles are right angles (each measuring $90°$).
A rectangle is a special type of parallelogram, which means it inherits all properties of parallelograms, plus has additional unique properties of its own.
🔑 Key Properties of a Rectangle
Sides & Angles
- ✅ Opposite sides are equal and parallel
- ✅ All four angles equal $90°$
- ✅ Consecutive angles are supplementary: $90° + 90° = 180°$
- ✅ Sum of all angles = $360°$
Diagonals
- ✅ Diagonals are equal in length
- ✅ Diagonals bisect each other (cut each other in half)
- ✅ Each diagonal divides the rectangle into two congruent right triangles
- ✅ Diagonals are NOT necessarily perpendicular (unless it's a square)