Binomial coefficient (n choose k) equals (n choose (n-k))

Theorem

The following formula holds: $${n \choose k} = {n \choose n-k},$$ where ${n \choose k}$ denotes the binomial coefficient.

References

• 1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): 3.1.3