Alphabeta Math
ExampleConstruction: Literature-sourcedVerification: AI-adaptedprecheck passaudited 2026-08-24
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Slicing gives the unit-ball volumes through dimension five

Example

Writing Vn:=Vn(1), slicing gives

V1=2,V2=π,V3=4π3,V4=π22,V5=8π215.

Facts & Assumptions

Given: Unit closed balls in positive integer dimensions.

[F1]

For n≥2, Vn=Vn−1∫−11(1−t2)(n−1)/2 dt (Closed Euclidean balls are Jordan measurable and their volumes satisfy the slicing recursion).

[F2]

The Wallis integrals satisfy I0=π/2, I1=1, and In=(n−1)In−2/n for n≥2 (Wallis integrals satisfy the two-step recurrence, closed forms, and the adjacent-integral squeeze).

Verification

technique · direct
1.1F1algebra

Starting with V1=2, [F1] and the upper-semicircle area give V2=π, while ∫−11(1−t2) dt=4/3 gives V3=4π/3.

2.1step 1.1F1F2algebra

With t=sin⁡θ, ∫−11(1−t2)3/2 dt=2∫0π/2cos⁡4θ dθ=3π/8 by [F2], giving V4=π2/2. Also ∫−11(1−t2)2 dt=16/15, giving V5=8π2/15.

3.1step 1.1step 2.1∎

Combining the preceding calculations gives the displayed table without using the Gamma closed form.

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

53 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.

Sources