BetaRegularized[z, a, b] \[Proportional] Piecewise[{{(Log[z] Sin[a Pi])/(E^(I a Pi) Pi), Arg[z] <= 0}}, (E^(I a Pi) Log[z] Sin[a Pi])/Pi] /; a + b == 1 && (Abs[z] -> Infinity)

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2007-05-02