let Z be open Subset of REAL ; :: thesis: ( Z c= dom ((tan + cot ) / exp_R ) implies ( (tan + cot ) / exp_R is_differentiable_on Z & ( for x being Real st x in Z holds
(((tan + cot ) / exp_R ) `| Z) . x = ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - (tan . x)) - (cot . x)) / (exp_R . x) ) ) )
A1: for x being Real st x in Z holds
exp_R . x <> 0 by SIN_COS:59;
assume Z c= dom ((tan + cot ) / exp_R ) ; :: thesis: ( (tan + cot ) / exp_R is_differentiable_on Z & ( for x being Real st x in Z holds
(((tan + cot ) / exp_R ) `| Z) . x = ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - (tan . x)) - (cot . x)) / (exp_R . x) ) )
then Z c= (dom (tan + cot )) /\ ((dom exp_R ) \ (exp_R " {0 })) by RFUNCT_1:def 4;
then A2: Z c= dom (tan + cot ) by XBOOLE_1:18;
then A3: tan + cot is_differentiable_on Z by Th6;
A4: exp_R is_differentiable_on Z by FDIFF_1:34, TAYLOR_1:16;
then A5: (tan + cot ) / exp_R is_differentiable_on Z by A3, A1, FDIFF_2:21;
for x being Real st x in Z holds
(((tan + cot ) / exp_R ) `| Z) . x = ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - (tan . x)) - (cot . x)) / (exp_R . x)

proof

let x be Real; :: thesis: ( x in Z implies (((tan + cot ) / exp_R ) `| Z) . x = ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - (tan . x)) - (cot . x)) / (exp_R . x) )
A6: exp_R is_differentiable_in x by SIN_COS:70;
A7: exp_R . x <> 0 by SIN_COS:59;
assume A8: x in Z ; :: thesis: (((tan + cot ) / exp_R ) `| Z) . x = ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - (tan . x)) - (cot . x)) / (exp_R . x)
then A9: (tan + cot ) . x = (tan . x) + (cot . x) by A2, VALUED_1:def 1;
tan + cot is_differentiable_in x by A3, A8, FDIFF_1:16;
then diff ((tan + cot ) / exp_R ),x = (((diff (tan + cot ),x) * (exp_R . x)) - ((diff exp_R ,x) * ((tan + cot ) . x))) / ((exp_R . x) ^2 ) by A6, A7, FDIFF_2:14
.= (((((tan + cot ) `| Z) . x) * (exp_R . x)) - ((diff exp_R ,x) * ((tan + cot ) . x))) / ((exp_R . x) ^2 ) by A3, A8, FDIFF_1:def 8
.= ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) * (exp_R . x)) - ((diff exp_R ,x) * ((tan + cot ) . x))) / ((exp_R . x) ^2 ) by A2, A8, Th6
.= ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) * (exp_R . x)) - ((exp_R . x) * ((tan . x) + (cot . x)))) / ((exp_R . x) * (exp_R . x)) by A9, SIN_COS:70
.= (((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - ((tan . x) + (cot . x))) * ((exp_R . x) / ((exp_R . x) * (exp_R . x)))
.= (((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - ((tan . x) + (cot . x))) * (((exp_R . x) / (exp_R . x)) / (exp_R . x)) by XCMPLX_1:79
.= (((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - ((tan . x) + (cot . x))) * (1 / (exp_R . x)) by A7, XCMPLX_1:60
.= (((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - ((tan . x) + (cot . x))) / (exp_R . x) ;
hence (((tan + cot ) / exp_R ) `| Z) . x = ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - (tan . x)) - (cot . x)) / (exp_R . x) by A5, A8, FDIFF_1:def 8; :: thesis: verum

end;

hence ( (tan + cot ) / exp_R is_differentiable_on Z & ( for x being Real st x in Z holds
(((tan + cot ) / exp_R ) `| Z) . x = ((((1 / ((cos . x) ^2 )) - (1 / ((sin . x) ^2 ))) - (tan . x)) - (cot . x)) / (exp_R . x) ) ) by A3, A4, A1, FDIFF_2:21; :: thesis: verum