 
Classifying quadrilateralsQuadrilateralsA quadrilateral is a polygon with 4 sides. It can be concave, or convex, simple, or complex, regular, or irregular but it must always have 4 straight lines for sides. Every quadrilateral has 4 sides (these are called edges), 4 corners (these are called vertices), and 4 angles. The angles inside a quadrilateral always add up to 360°. For example, in a rectangle, all 4 angles are 90° . 90° + 90° + 90° + 90° = 360° This is also true for every quadrilateral, not just rectangles. For example: In the quadrilateral given below, the measurements are:
Top left  92° Top right  66° Left  128° Bottom  74° Hence, the sum of the angles is: 92° + 66° + 128° + 74° = 360° Classifying Quadrilaterals Every 4sided figure is a quadrilateral, but there are some specific quadrilaterals. Lets discuss them: 1. Parallelogram A parallelogram has two pairs of parallel sides. (Parallel means the lines never cross – like railroad tracks). In a parallelogram, the sides across from each other are not only parallel but they are also the same size. 2. Rhombus A rhombus is a parallelogram that has 4 equal sides. That may sounds like we’re describing a square, but as you can see, a rhombus isn’t necessarily a square. A rhombus typically looks like a square that is slanted. 3. Square A square is a parallelogram with 4 equal sides and 4 right angles. (Remember right angles look like a perfect corner.) 4. Rectangle
A rectangle is a parallelogram with 4 right angles. Notice that the definition of a rectangle doesn’t say anything about the length of the sides. That’s because not all the sides are equal. However, because it says it’s a parallelogram, that means the sides opposite of each other will be equal. 5. Trapezoid A trapezoid has only one pair of parallel sides. Remember that a parallelogram had two pairs of parallel sides. In contrast, a trapezoid only has one pair. Also, there’s no guarantee that any of the sides are equal. 6.Kite A kite has two pairs of equal sides, but the equal sides are right next to each other. That’s different than a parallelogram, which has equal sides but they are across from each other. The diagonals of a kite (shown in the picture with dashed lines) always make a right angle. Summary Quadrilateral: A quadrilateral is a polygon with 4 sides. Types of Quadrilaterals Every 4sided figure is a quadrilateral, but there are some specific quadrilaterals: 1. A parallelogram has 2 pairs of parallel sides. 2. A rhombus is a parallelogram that has 4 equal sides. 3. A square is a parallelogram with 4 equal sides and 4 right angles. 4. A rectangle is a parallelogram with 4 right angles. 5. A trapezoid has only one pair of parallel sides. 6. A kite has two pairs of equal sides, but the equal sides are right next to each other. 
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