experimal error calc
x = s(sqrt((2(a+b))/zab)

There is error in s, a and b

show that it is equal to

$\displaystyle \Delta$ x/x = sqrt((1/(4ab)^2)*[(b$\displaystyle \Delta$a/a)^2+(a$\displaystyle \Delta$b/b)^2]+($\displaystyle \Delta$s/s)^2