theorem Th35: :: NDIFF_1:35

for S, T being RealNormSpace
for f1, f2 being PartFunc of S,T
for x0 being Point of S st f1 is_differentiable_in x0 & f2 is_differentiable_in x0 holds
( f1 + f2 is_differentiable_in x0 & diff ((f1 + f2),x0) = (diff (f1,x0)) + (diff (f2,x0)) )