Quadrilaterals - Four-Sided Polygons
Welcome to the fascinating world of quadrilaterals! These are special shapes that you see everywhere - from your book to your window, from floor tiles to playing cards.
1. What is a Quadrilateral?
Definition
A quadrilateral is a polygon with exactly:
- 4 sides (line segments)
- 4 vertices (corner points)
- 4 angles (at each corner)
Word Origin
"Quad" means four (like in "quadruple")
"Lateral" means sides
So quadrilateral = "four sides"
In Russian: четырёхугольник (four-angled figure)
Interactive visualization — available in the full lesson
2. Parts of a Quadrilateral
| Part | Description | In Russian |
|---|---|---|
| Vertices | 4 corner points: A, B, C, D | Вершины |
| Sides | 4 segments: AB, BC, CD, DA | Стороны |
| Angles | 4 angles: ∠A, ∠B, ∠C, ∠D | Углы |
| Diagonals | 2 segments: AC and BD | Диагонали |
Interactive visualization — available in the full lesson