The slant height of an object (such as a frustum, or pyramid) is the distance measured along a lateral face from the base to the apex along the "center" of the face. In other words, it is the altitude of the triangle comprising a lateral face (Kern and Bland 1948, p. 50).
The slant height 
of a right circular cone is the distance from the apex to a point on the base (Kern
and Bland 1948, p. 60), and is related to the height 
and base radius 
by
 |
For a right pyramid with a regular 
-gonal base of side length 
, the slant height is given by
 |
where 
is the inradius of the base.
