Derivatives of power function on ℂ
, ℝ
, ℝ≥0
, and ℝ≥0∞
#
THIS FILE IS SYNCHRONIZED WITH MATHLIB4. Any changes to this file require a corresponding PR to mathlib4.
We also prove differentiability and provide derivatives for the power functions x ^ y
.
Although λ x, x ^ r
for fixed r
is not complex-differentiable along the negative real
line, it is still real-differentiable, and the derivative is what one would formally expect.
This lemma says that λ x, a ^ x
is strictly differentiable for a < 0
. Note that these
values of a
are outside of the "official" domain of a ^ x
, and we may redefine a ^ x
for negative a
if some other definition will be more convenient.
The function (1 + t/x) ^ x
tends to exp t
at +∞
.
The function (1 + t/x) ^ x
tends to exp t
at +∞
for naturals x
.