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What is a Quadrilateral?
What is a quadrilateral?
Summary
- Closed shapes with four sides are called quadrilaterals
- Congruent sides are identified with matching dash marks
- Parallelograms are quadrilaterals whose opposite sides are congruent and parallel
- Rhombuses are parallelograms with all sides congruent
- Little boxes in the corner of a figure represent right angles
- Rectangles are parallelograms with four right angles
- Squares are parallelograms with four congruent sides and four right angles

Notes
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- A polygon is a closed figure whose sides are made up of line segments
- As long as it's a closed figure with four sides that are line segments, it's a quadrilateral!
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- Quadrilaterals with certain characteristics have special names
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- A parallelogram is a special type of quadrilateral
- Opposite sides congruent means that sides across from each other are the same length
- Angles that are across from each other in a parallelogram are equal too!
- Parallel means that if you extended out the sides forever in both directions, they would never cross
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- A rhombus is a special type of parallelogram, so it is also a quadrilateral
- All sides congruent means that all the sides are the same length
- Parallel means that if you extended out the sides forever in both directions, they would never cross
- Basically, a rhombus is a parallelogram with all sides equal
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- A rectangle is a special type of parallelogram, so it is also a quadrilateral
- Opposite sides congruent means that sides across from each other are the same length
- Parallel means that if you extended out the sides forever in both directions, they would never cross
- Right angles are angles that measure 90 degrees
- In the diagram, right angles are marked with a little box
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- A square is a special type of parallelogram, so it is also a quadrilateral
- All sides congruent means that all the sides are the same length
- Parallel means that if you extended out the sides forever in both directions, they would never cross
- Right angles are angles that measure 90 degrees
- In the diagram, right angles are marked with a little box
- Basically, a square is a rectangle with all sides equal
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- A trapezoid is a special type of quadrilateral
- Note that since only one pair of opposite sides are parallel, a trapezoid is NOT a parallelogram
- Parallelograms need BOTH pairs of opposite sides to be parallel
- Parallel means that if you extended out the sides forever in both directions, they would never cross