let Z be open Subset of REAL ; :: thesis: ( Z c= dom (cot * ln ) implies ( - (cot * ln ) is_differentiable_on Z & ( for x being Real st x in Z holds
((- (cot * ln )) `| Z) . x = 1 / (x * ((sin . (ln . x)) ^2 )) ) ) )
assume A1: Z c= dom (cot * ln ) ; :: thesis: ( - (cot * ln ) is_differentiable_on Z & ( for x being Real st x in Z holds
((- (cot * ln )) `| Z) . x = 1 / (x * ((sin . (ln . x)) ^2 )) ) )
then A2: Z c= dom (- (cot * ln )) by VALUED_1:8;
dom (cot * ln ) c= dom ln by RELAT_1:44;
then A4: Z c= dom ln by A1, XBOOLE_1:1;
A5: for x being Real st x in Z holds
x > 0

proof

let x be Real; :: thesis: ( x in Z implies x > 0 )
assume x in Z ; :: thesis: x > 0
then x in right_open_halfline 0 by A4, TAYLOR_1:18;
then ex g being Real st
( x = g & 0 < g ) by Lm1;
hence x > 0 ; :: thesis: verum

end;

A6: for x being Real st x in Z holds
sin . (ln . x) <> 0

proof

let x be Real; :: thesis: ( x in Z implies sin . (ln . x) <> 0 )
assume x in Z ; :: thesis: sin . (ln . x) <> 0
then ln . x in dom (cos / sin ) by A1, FUNCT_1:21;
hence sin . (ln . x) <> 0 by FDIFF_8:2; :: thesis: verum

end;

B: for x being Real st x in Z holds
diff ln ,x = 1 / x

proof

let x be Real; :: thesis: ( x in Z implies diff ln ,x = 1 / x )
assume x in Z ; :: thesis: diff ln ,x = 1 / x
then x > 0 by A5;
then x in right_open_halfline 0 by Lm1;
hence diff ln ,x = 1 / x by TAYLOR_1:18; :: thesis: verum

end;

A8: cot * ln is_differentiable_on Z by A1, FDIFF_8:15;
then A9: (- 1) (#) (cot * ln ) is_differentiable_on Z by A2, FDIFF_1:28, A;
for x being Real st x in Z holds
((- (cot * ln )) `| Z) . x = 1 / (x * ((sin . (ln . x)) ^2 ))

proof

let x be Real; :: thesis: ( x in Z implies ((- (cot * ln )) `| Z) . x = 1 / (x * ((sin . (ln . x)) ^2 )) )
assume A10: x in Z ; :: thesis: ((- (cot * ln )) `| Z) . x = 1 / (x * ((sin . (ln . x)) ^2 ))
then A11: ln is_differentiable_in x by A5, TAYLOR_1:18;
A12: ( x > 0 & sin . (ln . x) <> 0 ) by A5, A6, A10;
then A13: cot is_differentiable_in ln . x by FDIFF_7:47;
A14: cot * ln is_differentiable_in x by A8, A10, FDIFF_1:16;
((- (cot * ln )) `| Z) . x = diff (- (cot * ln )),x by A9, A10, FDIFF_1:def 8
.= (- 1) * (diff (cot * ln ),x) by A14, FDIFF_1:23, A
.= (- 1) * ((diff cot ,(ln . x)) * (diff ln ,x)) by A11, A13, FDIFF_2:13
.= (- 1) * ((- (1 / ((sin . (ln . x)) ^2 ))) * (diff ln ,x)) by A12, FDIFF_7:47
.= (- 1) * (- ((diff ln ,x) / ((sin . (ln . x)) ^2 )))
.= (- 1) * (- ((1 / x) / ((sin . (ln . x)) ^2 ))) by B, A10
.= 1 / (x * ((sin . (ln . x)) ^2 )) by XCMPLX_1:79 ;
hence ((- (cot * ln )) `| Z) . x = 1 / (x * ((sin . (ln . x)) ^2 )) ; :: thesis: verum

end;

hence ( - (cot * ln ) is_differentiable_on Z & ( for x being Real st x in Z holds
((- (cot * ln )) `| Z) . x = 1 / (x * ((sin . (ln . x)) ^2 )) ) ) by A2, A8, FDIFF_1:28, A; :: thesis: verum