Alphabeta Math
DefinitionDefinition: Literature-sourcedProof: Not applicableSession-authored (Fable 5 assisted)audited 2026-08-03
How statement and proof provenance work

The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.

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The principal inverse tangent arctan:R(π/2,π/2)\arctan:\mathbb R\to(-\pi/2,\pi/2)

Definition

By Tangent is a continuous strictly increasing bijection from (π/2,π/2)(-\pi/2,\pi/2) onto R\mathbb R, tangent restricts to a continuous strictly increasing bijection

tan:(π/2,π/2)R.\tan:(-\pi/2,\pi/2)\longrightarrow\mathbb R.

Its inverse is the principal inverse tangent

arctan:R(π/2,π/2).\arctan:\mathbb R\longrightarrow(-\pi/2,\pi/2).

Thus tan(arctany)=y\tan(\arctan y)=y for every real yy, while arctan(tanx)=x\arctan(\tan x)=x precisely for xx in the displayed principal interval. The inverse is continuous and strictly increasing by Continuous inverse theorem: a continuous injective ff on an interval II is a bijection onto the order-convex set f[I]f[I], and the inverse g:f[I]Ig : f[I] \to I is continuous and strictly monotone in the same sense as ff.

Depends on

Used by

Dependency tree · next 3 levels

Direct dependencies and their dependencies through the next three levels: 69 results over 22 levels. An arrow runs from a result to what uses it, and this result sits at the bottom with a heavier outline. Click the chart to enlarge it.

Sources