Differentiable function/D in R/Linear approximation/Fact
Let be a subset, a point, and
a function.
Then is
differentiable in if and only if there exists some and a function
such that is continuous in , , and such that
Let be a subset, a point, and
a function.
differentiable in if and only if there exists some and a function
such that is continuous in , , and such that