Digamma at 1
From specialfunctionswiki
Theorem
The following formula holds: $$\psi(1)=-\gamma,$$ where $\psi$ denotes the digamma function and $\gamma$ denotes the Euler-Mascheroni constant.
Proof
References
- 1953: Arthur Erdélyi, Wilhelm Magnus, Fritz Oberhettinger and Francesco G. Tricomi: Higher Transcendental Functions Volume I ... (previous) ... (next): $\S 1.7 (4)$
- 1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): $6.3.2$
