theorem :: FDIFF_3:13

for f1, f2 being PartFunc of REAL,REAL
for x0 being Real st f1 is_left_differentiable_in x0 & f2 is_left_differentiable_in x0 & f2 . x0 <> 0 holds
( f1 / f2 is_left_differentiable_in x0 & Ldiff ((f1 / f2),x0) = (((Ldiff (f1,x0)) * (f2 . x0)) - ((Ldiff (f2,x0)) * (f1 . x0))) / ((f2 . x0) ^2) )