Wallis integral: sine power on [0,π/2] (Wallis: ∫_0^{π/2} sin^n x = product formula (odd/even n).)

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Wallis: ∫_0^{π/2} sin^n x = product formula (odd/even n).

What each symbol means

SymbolWhat it stands for
nNon-negative integer

When to use this

W_n = ((n-1)/n) W_{n-2} with base W_0=π/2, W_1=1.