However when either a or b are large (typically above 8) then there are more appropriate methods of computing an accurate value efficiently.
An illustration of this curve is given below:
Graph is not currently available
References:
DiDinato, A. R. and Morris, A. H. Algorithm 708: Significant Digit Computation of the Incomplete Beta Function Ratios. ACM Trans. Math. Softw. 18 (1993), 360-373.
Parameters
a
first symmetric argument to the complete beta function, a>0.
b
second symmetric argument to the complete beta function, b>0.