These functions provide approximate measures of length, area, and volume of geometries where relevant. The reason for approximation is that some measures require square root operations or multiplication by π, both operations where exactness is necessarily lost. Not all geometries have meaningful measures, e.g. a direction is dimensionless, a line is without area, and a circle has no volume. Some geometries are infinite in some measures, e.g. a plane has an infinite area. The return value will reflect this.

## See also

Other Measures:
`approx_angle()`

,
`distance_squared()`