# Side length

The side length is a special case of the length of a line in geometry . The side lengths of a polygon (polygon) are the distances between the respective two corners . The sum of all side lengths is the circumference .

## Side length of triangles

### Triangle sides in geometry and nature

The length of the sides of the triangle (in the case of flat triangles) is specified in a measure of length (mainly in meters, cm and km). But if you go from the usual geometry to nature or to trigonometric tasks of geodesy , a distinction must be made between horizontal and inclined sides:

### Euclidean geometry

• A well-known Euclidean theorem states that the longest side of a triangle is always shorter than the sum of the other two sides ( triangle inequality ).
• The larger of two sides of a triangle is always opposite the larger angle. Conversely, the larger of two angles of a triangle is always opposite the longer side.

### Plane triangles and their special cases

Right triangle with the right angle at point C.

### Spherical triangles

In spherical geometry (spherical geometry), the side length initially corresponds to the length of the corresponding great circle arc . Most of the time, however, the size of the corresponding center angle (in degrees ) is taken as the side length. This definition has the advantage that the radius of the sphere does not matter.

## Side length of polygons

The length of the sides of general polygons can be traced back to the calculations on the triangle via the diagonals .