Paper 2, Section II, E

Further Complex Methods | Part II, 2013

The Beta function is defined for Re(z)>0\operatorname{Re}(z)>0 as

B(z,q)=01tq1(1t)z1dt,(Re(q)>0)B(z, q)=\int_{0}^{1} t^{q-1}(1-t)^{z-1} d t, \quad(\operatorname{Re}(q)>0)

and by analytic continuation elsewhere in the complex zz-plane.

Show that:

(i) (z+q)B(z+1,q)=zB(z,q)(z+q) B(z+1, q)=z B(z, q);

(ii) Γ(z)2=B(z,z)Γ(2z)\Gamma(z)^{2}=B(z, z) \Gamma(2 z).

By considering Γ(z/2m)\Gamma\left(z / 2^{m}\right) for all positive integers mm, deduce that Γ(z)0\Gamma(z) \neq 0 for all zz with Re(z)>0\operatorname{Re}(z)>0.

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