theorem Th2: :: INTEGR14:2

for Z being open Subset of REAL st Z c= dom (cosec * exp_R) holds
( - (cosec * exp_R) is_differentiable_on Z & ( for x being Real st x in Z holds
((- (cosec * exp_R)) `| Z) . x = ((exp_R . x) * (cos . (exp_R . x))) / ((sin . (exp_R . x)) ^2) ) )