theorem :: DIFF_3:41

for h, x being Real
for f being Function of REAL,REAL st ( for x being Real holds f . x = sqrt x ) & x + (h / 2) > 0 & x - (h / 2) > 0 holds
(cD (f,h)) . x = (sqrt (x + (h / 2))) - (sqrt (x - (h / 2)))