# What is a diagonal?

The diagonal has a geometric meaning in mathematics. Diagonal is distinguished in different polygons, it helps in calculating the areas of figures. It is used to describe matrices, more square. That's why it's so important to know what a diagonal is. In the study of polygons and polyhedra, the diagonal is a segment that connects two vertices that do not lie on one side. For example, a quadrilateral has two diagonals that connects two opposing vertices. If the polygon is convex, then the diagonals pass inside.

And if we talk about the diagonal in a square or inrectangle? First, let's remember the Pythagorean theorem, the essence of which is that the square of the hypotenuse is equal to the sum of the squares of the legs. The diagonal in a square and in a rectangle divides it into two identical rectangular triangles. The adjacent sides are the legs, and the diagonal is the hypotenuse. Consequently, the sum of the squares of the two sides (adjacent) is equal to the square of the diagonal. In the end, it remains only to extract the root from the sum of the squares of the legs and get the value of the diagonal.

Now you know what a diagonal in geometry is and what it means.