Summary

A diagonal of a parallelogram divides it into two congruentincongruentsimilar triangles.

In a parallelogram:

opposite sides are equalnot equal

opposite angles are equalnot equal

diagonals bisectsimilar each other

Diagonals of a rectangle bisect each other bisect each other at right angles and are equalnot equal and vice-versa.

Diagonals of a rhombusbisect each other at right anglesbisect each other and vice-versa.

Diagonals of a square bisect each other at rightleft angles and are equalnot equal, and vice-versa.

The line-segment joining the mid-points of any two sides of a triangle is parallelbisect to the third side and is halfright of it.

A line through the mid-point of a side of a triangle parallel to another side bisectsparallel the third side.