At the solution of various geometrical tasks quite often it is required to find the area of a triangle or figures which can be presented in the scheme of several triangles. Sometimes the area of this figure is required to be calculated also in life. For determination of the area there are several ways, application of each of which is defined by a type of a triangle and its known parameters.

Apparently in the drawing, the triangle which two sides are equal is isosceles. It is possible to find the area of an isosceles triangle, knowing length of its basis and height or on length of its basis and any side of a triangle.

Before we consider various ways of finding of a leg in a rectangular triangle, we will accept some designations. A leg call the party of a rectangular triangle, adjacent to a right angle. Lengths of legs we will conditionally designate an and b. Corners, opposite to legs of an and b we will designate respectively through A and B. The hypotenuse, by definition, is the party of a rectangular triangle which is opposite to a right angle (at the same time with other parties of a triangle the hypotenuse forms acute angles). We will designate length of a hypotenuse through page.

Parallelepiped – figures volume, characterized by existence of sides and edges. Each side side is formed by two parallel side edges and the parties of both bases corresponding each other. To find a side surface of a parallelepiped, it is necessary to put the areas of all of its vertical or inclined parallelograms.