ABCD-parallelogram, M and N – midpoints of BC and AD sides. Prove that a quadrilateral is an AMCN-parallelogram.

By condition, ABCD is a parallelogram, therefore AD = BC, and they are parallel, which means that the MC and ND segments are also parallel, since they lie on these straight lines. Points M and N are the middle of the segments, therefore BM = MC, a AN = ND, and since BC = AD, then MC = AN.

Thus, the segments MC and AN are equal and parallel.

If in a quadrilateral two sides are equal and parallel, then this quadrilateral is a parallelogram.

Q.E.D.



One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.