Power function on ℝ≥0
and ℝ≥0∞
#
We construct the power functions x ^ y
where
x
is a nonnegative real number andy
is a real number;x
is a number from[0, +∞]
(a.k.a.ℝ≥0∞
) andy
is 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
.
Equations
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
).
Equations
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