Inverse of the incomplete beta integral.
Syntax:		@betaincinv(x, a, b, p)
	p:	number
	a:	number
	b	number
Return:		number
Returns the x satisfying the incomplete beta integral for elements of p, a and b:
for 

 and 

.
Examples
= @betaincinv(0.5,2,2)
returns 0.5.
Cross-references