Classifying polygons
Topic Notes
In this lesson, we will learn:
- A quadrilateral is a polygon with 4 sides
- We can look at the properties of a quadrilateral (pairs of parallel sides, pairs of congruent sides, types of angles) to classify into 6 different types
- The special types of quadrilaterals are: rectangle, square, parallelogram, rhombus, trapezoid, and kite
Notes:
- A quadrilateral is a 2D shape with 4 straight sides (a 4-sided polygon)
- A quadrilateral also has 4 vertices (corners)
- Each corner contains an angle; the total angle sum in any quadrilateral is 360°
- There are special quadrilaterals with specific definitions and names
- There will be 6 types of quadrilaterals in this lesson: Rectangle, Square, Parallelogram, Rhombus, Trapezoid, and Kite
- A quadrilateral can fit the definition of more than one of these special types
- Rectangles and squares:
- Quadrilaterals with 4 right angles (all angles are 90° )
- A rectangle has 2 pairs of opposite and equal sides (congruent)
- A square is a special type of rectangle where all 4 sides are equal (congruent)
- All squares are rectangles, but not all rectangles are squares
- Rectangles and squares can also be considered as parallelograms, just with right angles
- Parallelograms and rhombuses:
- Quadrilaterals with 2 pairs of parallel sides and 2 pairs of opposite equal angles
- A parallelogram has 2 pairs of congruent sides (equal length)
- A rhombus has all 4 sides congruent (all 4 sides equal length)
- All rhombuses are parallelograms; not all parallelograms are rhombuses
- Trapezoids:
- Quadrilaterals with only 1 pair of parallel sides
- Kites:
- Quadrilaterals with 2 adjacent congruent sides (no parallel sides)
- There is 1 pair of opposite equal angles across the line of symmetry
- Summary of quadrilateral types and properties (sides and angles):
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