The function x ↦ - x * log x
#
The purpose of this file is to record basic analytic properties of the function x ↦ - x * log x
,
which is notably used in the theory of Shannon entropy.
Main definitions #
negMulLog
: the functionx ↦ - x * log x
fromℝ
toℝ
.
theorem
Real.hasDerivAt_mul_log
{x : ℝ}
(hx : x ≠ 0)
:
HasDerivAt (fun (x : ℝ) => x * x.log) (x.log + 1) x