For a locally Lipschitz continuous function f ⁣:X→Rf\colon X\to\mathbb{R} the generalized gradient ∂f(x)\partial f(x) of Clarke is used to develop some (set-valued) gradient on a set A⊂XA\subset X. Existence, uniqueness and some approximation are considered for optimal descent directions on set AA. The results serve as basis for nonsmooth numerical descent algorithms that can be found in subsequent papers.

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