Теория:

A quadrilateral whose opposite sides are parallel in pairs is called a parallelogram.
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Properties of a parallelogram
The opposite sides of the parallelogram are of equal length in pairs.
 
\(AB = DC\)
 
\( BC = AD\)
 
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The opposite angles of a parallelogram are equal in size.
 
\(A =\)\(C\)
 
\(B =\)\(D\)
 
3.png
The parallelogram divides at the intersection of the diagonal in half.
 
\(BO = OD\)
 
\(AO = OC\)
 
4.png
The diagonal of parallelogram divides it into two equal triangles.
 
Triangles \(ABC\) and \(CDA\) are equal.
 
4.png
The sum of the angles on each side of the parallelogram is \(180\) degrees.
 
\(A +\)\(D = 180\) degrees
 
6.png
The transverse angles at the diagonal are the same.
 
\(BAC =\)\(ACD\)
 
\(BCA =\)\(CAD\)
 
7.png