(Pre)images of intervals #
In this file we prove a bunch of trivial lemmas like “if we add a to all points of [b, c],
then we get [a + b, a + c]”. For the functions x ↦ x ± a, x ↦ a ± x, and x ↦ -x we prove
lemmas about preimages and images of all intervals. We also prove a few lemmas about images under
x ↦ a * x, x ↦ x * a and x ↦ x⁻¹.
Preimages under x ↦ a + x #
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Preimages under x ↦ x + a #
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Preimages under x ↦ -x #
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Preimages under x ↦ x - a #
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Preimages under x ↦ a - x #
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Images under x ↦ a + x #
Images under x ↦ x + a #
Images under x ↦ -x #
Images under x ↦ a - x #
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Images under x ↦ x - a #
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Bijections #
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theorem
Set.abs_sub_le_of_uIcc_subset_uIcc
{α : Type u_1}
[LinearOrderedAddCommGroup α]
{a : α}
{b : α}
{c : α}
{d : α}
(h : Set.uIcc c d ⊆ Set.uIcc a b)
:
If [c, d] is a subinterval of [a, b], then the distance between c and d is less than or
equal to that of a and b
theorem
Set.abs_sub_left_of_mem_uIcc
{α : Type u_1}
[LinearOrderedAddCommGroup α]
{a : α}
{b : α}
{c : α}
(h : c ∈ Set.uIcc a b)
:
If c ∈ [a, b], then the distance between a and c is less than or equal to
that of a and b
theorem
Set.abs_sub_right_of_mem_uIcc
{α : Type u_1}
[LinearOrderedAddCommGroup α]
{a : α}
{b : α}
{c : α}
(h : c ∈ Set.uIcc a b)
:
If x ∈ [a, b], then the distance between c and b is less than or equal to
that of a and b
Multiplication and inverse in a field #
The (pre)image under inv of Ioo 0 a is Ioi a⁻¹.