Let a space curve have line elements , 
, and 
 along the normal, tangent, and binormal vectors respectively,
 then
| 
 
(1)
 
 | 
where
| 
 
(2)
 
 | |||
| 
 
(3)
 
 | |||
| 
 
(4)
 
 | 
Let a space curve have line elements , 
, and 
 along the normal, tangent, and binormal vectors respectively,
 then
| 
 
(1)
 
 | 
where
| 
 
(2)
 
 | |||
| 
 
(3)
 
 | |||
| 
 
(4)
 
 | 
Weisstein, Eric W. "Lancret Equation." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/LancretEquation.html