English
An alternate specialization of the left-mulation derivative equivalence for smul and composition.
Русский
Альтернативная специализация эквивалентности производной слева для умножения и композиции.
LaTeX
$$$$Eq (HasDerivWithinAt f f' (c \cdot s) (c \cdot x)) (HasDerivWithinAt (fun x => f (c x)) (c f') s x)$$$$
Lean4
theorem derivWithin_comp_mul_left : derivWithin (f <| c * ·) s x = c • derivWithin f (c • s) (c * x) :=
by
simp only [← smul_eq_mul]
rw [← derivWithin_const_smul', derivWithin, derivWithin, fderivWithin_comp_smul_eq_fderivWithin_smul, Pi.smul_def]