Read the result
The result panel first reports the direct-substitution form. Only an indeterminate form unlocks the derivative step.
Limits and errors
L'Hopital Limit Checker
Check a quotient limit before applying L'Hopital's rule.
Formula
lim f(x)/g(x) = lim f'(x)/g'(x) when the rule's conditions apply
Result
Worked substitution
The first step is not differentiation. The first step is checking the original quotient.
Where it helps
Use it to avoid the common habit of differentiating quotients too early.
Common slip
L'Hopital's rule is not for ordinary non-zero-over-non-zero substitution.
Try it
Compare sin x / x with x / (1+x). Only one needs L'Hopital at x = 0.