theorem Th50: :: INTEGR13:50

for Z being open Subset of REAL st Z c= dom (exp_R * arccot) & Z c= ].(- 1),1.[ holds
( - (exp_R * arccot) is_differentiable_on Z & ( for x being Real st x in Z holds
((- (exp_R * arccot)) `| Z) . x = (exp_R . (arccot . x)) / (1 + (x ^2)) ) )