Diagonals of a quadrangle connect its opposite tops, dividing a figure into couple of triangles. To find the big diagonal of a parallelogram, it is necessary to make a number of calculations according to initial data of a task.

Parallelepiped – the many-sided geometrical figure having several interesting properties. Knowledge of these properties helps with the solution of tasks. There is, for example, a certain communication between its linear and diagonal measurements by means of which it is possible to find lengths of edges of a parallelepiped on diagonal.

In a quadrangle of tops opposite each other the creation of its diagonals is result of connection. There is a general formula connecting lengths of these pieces with another dimensions of a figure. On it, in particular, it is possible to find parallelogram diagonal length.

Parallelepiped - a special case of a prism at which all six sides are parallelograms or rectangles. The parallelepiped with rectangular sides is called also rectangular. The parallelepiped has four crossed diagonals. If three edges are given and, b, with, can find all diagonals of a rectangular parallelepiped, carrying out additional constructions.