I have to prove this equality $$\Gamma(\frac{1}{2}-x)\Gamma(\frac{1}{2}+x)=\frac{\pi}{\cos\pi x}$$ I assume, since both Gamma's have $\frac12$ as part of their argument, I'll have to use the fact that $\Gamma(\frac12)=\sqrt\pi$ I just don't know how. I also thought of using $\Gamma(x)\Gamma(1-x)=\frac{\pi}{\sin\pi x}$.
Asked
Active
Viewed 470 times
2
-
2Your last sentence is the thing to do: just a $\frac12$ shift! – Jean Marie May 30 '21 at 13:19
-
Oh my, It's so obvious. How could I not see this. Thanks a lot. – Dio May 30 '21 at 13:20
-
1It happens to me rather often as well... – Jean Marie May 30 '21 at 13:27
-
This will help you : https://math.stackexchange.com/questions/2159079/what-is-gamma1-2-n-gamma1-2n – p_square May 30 '21 at 13:49
1 Answers
2
Putting an answer here for the sake of closing the question.
Since $$\Gamma(x)\Gamma(1-x)=\frac{\pi}{\sin\pi x},$$ it follows that $$\Gamma(\tfrac{1}{2}-x)\Gamma(\tfrac{1}{2}+x)=\Gamma(\tfrac{1}{2}-x)\Gamma(1-(\tfrac{1}{2}-x))=\frac{\pi}{\sin\pi(\tfrac{1}{2}-x)}=\frac{\pi}{\cos\pi x},$$ which is the desired solution.
Aaron Hendrickson
- 6,042