53, Special Quadrilaterals

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5-3, Special Quadrilaterals

• Objectives
• Distinguish quadrilaterals from other polygons
• Identify specific quadrilaterals, including
  parallelograms, rectangles, rhombuses,
  trapezoids, and squares

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Quadrilateral Vocabulary

• Parallelogram a quadrilateral whose opposite
  sides are parallel
• Rectangle a parallelogram with four right angles

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Quadrilateral Vocabulary

• Rhombus a parallelogram with four equal sides
• Trapezoid a quadrilateral with exactly one pair
  of parallel sides

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Counterexample A single example that proves a
statement false

• To prove a statement such as All boys play
  football is false, all that is needed is the
  statement one boy does not play football.
• Can you think of a
• counterexample?

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Examples

• Statement All trapezoids are isosceles.
• Question Is this statement true?
• Answer No. It is possible to construct a
  trapezoid that does not have a pair of equal
  sides and so it is not isosceles.
  (counterexample)

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Examples

• Statement All parallelograms are rectangles.
• Question Is this statement true?
• Answer No. You can construct a parallelogram
  that is not a rectangle. (The counterexample
  proves this to be false.

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5-3, Special Quadrilaterals
Date _______________________

• Objectives
• Distinguish quadrilaterals from other polygons
• Identify specific quadrilaterals, including
  parallelograms, rectangles, rhombuses,
  trapezoids, and squares

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Quadrilateral Vocabulary

• _____________ a quadrilateral whose opposite
  sides are parallel
• ______________ a parallelogram with four right
  angles

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Quadrilateral Vocabulary

• _______________ a parallelogram with four equal
  sides
• _______________ a quadrilateral with exactly one
  pair of parallel sides

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___________ A single example that proves a
statement false

• To prove a statement such as All boys play
  football is false, all that is needed is the
  statement one boy does not play football.
• Can you think of a
• counterexample?

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Examples

• Statement All trapezoids are isosceles.
• Question Is this statement true?
• Answer

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Examples

• Statement All parallelograms are rectangles.
• Question Is this statement true?
• Answer

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