🔢 Classifying 2D Figures

What is a Quadrilateral?
A quadrilateral is a polygon with 4 sides and 4 angles.
Quadrilateral Family Tree:
QUADRILATERAL
(4 sides, 4 angles)
│
┌────────────────┼────────────────┐
│ │ │
TRAPEZOID PARALLELOGRAM (Other: kite, etc.)
(1 pair of (2 pairs of parallel
parallel sides)
sides) │
┌────────────┼────────────┐
│ │ │
RECTANGLE RHOMBUS SQUARE?
(4 right (4 equal sides, (special case!)
angles) not right angles)
│ │
└──────┬─────┘
│
SQUARE
(4 right angles + 4 equal sides)Quadrilateral Hierarchy:
ShapePropertiesTrapezoid1 pair of parallel sidesParallelogram2 pairs of parallel sides, opposite sides equalRectangleParallelogram + 4 right anglesRhombusParallelogram + 4 equal sidesSquareRectangle + Rhombus (4 right angles + 4 equal sides)

What is a Triangle?
A triangle is a polygon with 3 sides and 3 angles. Sum of angles = 180°.
Classification by Sides:
TypeDescriptionExampleEquilateralAll 3 sides EQUAL3 cm, 3 cm, 3 cmIsosceles2 sides EQUAL5 cm, 5 cm, 3 cmScaleneNO sides equal4 cm, 5 cm, 6 cmClassification by Angles:
TypeDescriptionExampleAcuteAll angles < 90°60°, 60°, 60°RightOne angle = 90°30°, 60°, 90°ObtuseOne angle > 90°30°, 30°, 120°