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 MathWorldA Wolfram Web Resource. https://mathworld.wolfram.com/LancretEquation.html