I ask about an idea to prove this formula:

$Γ(1/2-iβ)=((√π)/(√(coshπβ)))exp(-i(2ϑ(β)+βln2π+arctan(tanh(1/2)πβ)))$

where $ϑ(β)$ is the Riemann Siegel function.

I ask about an idea to prove this formula:

$Γ(1/2-iβ)=((\sqrt{π})/(\sqrt{\coshπβ}))\exp(-i(2ϑ(β)+βln2π+\arctan(\tanh(1/2)πβ)))$

where $ϑ(β)$ is the Riemann Siegel function.