Power function on ℝ≥0 and ℝ≥0∞ #
We construct the power functions x ^ y where
xis a nonnegative real number andyis a real number;xis a number from[0, +∞](a.k.a.ℝ≥0∞) andyis a real number.
We also prove basic properties of these functions.
The nonnegative real power function x^y, defined for x : ℝ≥0 and y : ℝ as the
restriction of the real power function. For x > 0, it is equal to exp (y log x). For x = 0,
one sets 0 ^ 0 = 1 and 0 ^ y = 0 for y ≠ 0.
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Instances For
@[simp]
@[simp]
rpow version of Multiset.prod_map_pow for ℝ≥0.
theorem
Real.multiset_prod_map_rpow
{ι : Type u_1}
(s : Multiset ι)
(f : ι → ℝ)
(hs : ∀ i ∈ s, 0 ≤ f i)
(r : ℝ)
:
rpow version of Multiset.prod_map_pow.
theorem
NNReal.rpow_left_injective
{x : ℝ}
(hx : x ≠ 0)
:
Function.Injective fun (y : NNReal) => y ^ x
theorem
NNReal.rpow_left_surjective
{x : ℝ}
(hx : x ≠ 0)
:
Function.Surjective fun (y : NNReal) => y ^ x
theorem
NNReal.rpow_left_bijective
{x : ℝ}
(hx : x ≠ 0)
:
Function.Bijective fun (y : NNReal) => y ^ x
@[simp]
The real power function x^y on extended nonnegative reals, defined for x : ℝ≥0∞ and
y : ℝ as the restriction of the real power function if 0 < x < ⊤, and with the natural values
for 0 and ⊤ (i.e., 0 ^ x = 0 for x > 0, 1 for x = 0 and ⊤ for x < 0, and
⊤ ^ x = 1 / 0 ^ x).
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Instances For
@[simp]
@[simp]
theorem
ENNReal.rpow_left_injective
{x : ℝ}
(hx : x ≠ 0)
:
Function.Injective fun (y : ENNReal) => y ^ x
theorem
ENNReal.rpow_left_surjective
{x : ℝ}
(hx : x ≠ 0)
:
Function.Surjective fun (y : ENNReal) => y ^ x
theorem
ENNReal.rpow_left_bijective
{x : ℝ}
(hx : x ≠ 0)
:
Function.Bijective fun (y : ENNReal) => y ^ x