# 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): $6.3.2$