Multiplicative operations on derivatives #
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For detailed documentation of the Fréchet derivative,
see the module docstring of analysis/calculus/fderiv/basic.lean
.
This file contains the usual formulas (and existence assertions) for the derivative of
- multiplication of a function by a scalar function
- multiplication of two scalar functions
- inverse function (assuming that it exists; the inverse function theorem is in
../inverse.lean
)
Derivative of the pointwise composition/application of continuous linear maps #
Derivative of the product of a scalar-valued function and a vector-valued function #
If c
is a differentiable scalar-valued function and f
is a differentiable vector-valued
function, then λ x, c x • f x
is differentiable as well. Lemmas in this section works for
function c
taking values in the base field, as well as in a normed algebra over the base
field: e.g., they work for c : E → ℂ
and f : E → F
provided that F
is a complex
normed vector space.
Derivative of the product of two functions #
At an invertible element x
of a normed algebra R
, the Fréchet derivative of the inversion
operation is the linear map λ t, - x⁻¹ * t * x⁻¹
.
Derivative of the inverse in a division ring #
Note these lemmas are primed as they need complete_space R
, whereas the other lemmas in
deriv/inv.lean
do not, but instead need nontrivially_normed_field R
.
At an invertible element x
of a normed division algebra R
, the Fréchet derivative of the
inversion operation is the linear map λ t, - x⁻¹ * t * x⁻¹
.
Non-commutative version of fderiv_inv
Non-commutative version of fderiv_within_inv