Alphabeta Math
ExampleConstruction: Literature-sourcedVerification: AI-adaptedSession-authored (Fable 5 assisted)precheck 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 n2, Vn=Vn111(1t2)(n1)/2dt (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=(n1)In2/n for n2 (Wallis integrals satisfy the two-step recurrence, closed forms, and the adjacent-integral squeeze).

Verification

technique · direct
1.1

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

F1algebra
2.1

With t=sinθ, 11(1t2)3/2dt=20π/2cos4θdθ=3π/8 by [F2], giving V4=π2/2. Also 11(1t2)2dt=16/15, giving V5=8π2/15.

step 1.1F1F2algebra
3.1

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

step 1.1step 2.1

Depends on

Used by

Nothing in the library uses this result yet.

Dependency tree · two levels

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Sources