Theory:

A parallelogram is a flat shape quadrilateral with opposite sides parallel and equal in length.
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Where \(|\) and \(||\) denotes equal sides.
 
Properties of parallelogram:
  • Opposite sides are parallel.
  • Opposite sides are equal in length.
  • Opposite angles are equal. (Angles \(A\) and \(D\) are the same, and angles \(B\) and \(C\) are the same.)
  • Adjacent angles are supplementary. Angles \(A\) and \(B\) or \(C\) and \(D\) add up to \(180°\).
Important!
A parallelogram can be a square, rectangle, and rhombus with some conditions.
 
For example, A parallelogram became a rectangle where all angles are right angles.
 
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