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| Parallelograms |
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| Parallelogram is a quadrilateral whose opposite sides are parallel and equal. |
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| A rectangle, a rhombus and a square are considered as parallelograms. |
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| A trapezoid is quadrilateral with exactly one pair of opposite sides being parallel. Hence, it is not a parallelogram. |
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| You have learnt a few properties of parallelogram through measurement. Recall the properties of a parallelogram. |
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 Each pair of opposite sides are equal and parallel. |
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| In the diagram, |
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| Opposite sides: AB||DC and AD||BC |
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| AB=DC and AD=BC |
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 Opposite angles are equal. |
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 Diagonals of a parallelogram bisect each other. |
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| In the diagram, OD=OB and OA=OC |
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 Each diagonal divides the parallelogram into two congruent triangles. |
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| The properties of a parallelogram understood through measurement can also be proved through logical steps. But, before that let us recall some names associated with pairs of sides and angles of a quadrilateral. |
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 Opposite sides of a quadrilateral: |
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| Two sides of a quadrilateral, which have no common point, are called opposite sides. |
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| In the diagram, AB and DC is one pair of opposite sides. |
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| AD and BC is the other pair of opposite sides. |
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 Consecutive sides of a quadrilateral: |
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| Two sides of a quadrilateral, which have a common end point, are called consecutive sides. In the diagram, |
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| AB and BC is one pair of consecutive sides. |
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| BC, CD; CD, DA; and DA, AB are the other three pairs of consecutive sides. |
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 Opposite angles of a quadrilateral: |
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| Two angles, which do not include a side in their intersection, are called the opposite angles of a quadrilateral. |
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 Consecutive angles of a quadrilateral: |
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| Two angles of a quadrilateral, which include a side in their intersection, are called consecutive angles. |
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