let Z be open Subset of REAL; :: thesis: for g being PartFunc of REAL,REAL st not 0 in Z & Z c= dom (g (#) (cos * ((id Z) ^))) & g = #Z 2 holds
( g (#) (cos * ((id Z) ^)) is_differentiable_on Z & ( for x being Real st x in Z holds
((g (#) (cos * ((id Z) ^))) `| Z) . x = ((2 * x) * (cos . (1 / x))) + (sin . (1 / x)) ) )
let g be PartFunc of REAL,REAL; :: thesis: ( not 0 in Z & Z c= dom (g (#) (cos * ((id Z) ^))) & g = #Z 2 implies ( g (#) (cos * ((id Z) ^)) is_differentiable_on Z & ( for x being Real st x in Z holds
((g (#) (cos * ((id Z) ^))) `| Z) . x = ((2 * x) * (cos . (1 / x))) + (sin . (1 / x)) ) ) )
set f = id Z;
assume that
A1: not 0 in Z and
A2: Z c= dom (g (#) (cos * ((id Z) ^))) and
A3: g = #Z 2 ; :: thesis: ( g (#) (cos * ((id Z) ^)) is_differentiable_on Z & ( for x being Real st x in Z holds
((g (#) (cos * ((id Z) ^))) `| Z) . x = ((2 * x) * (cos . (1 / x))) + (sin . (1 / x)) ) )
A4: for x being Real st x in Z holds
g is_differentiable_in x by A3, TAYLOR_1:2;
A5: Z c= (dom g) /\ (dom (cos * ((id Z) ^))) by A2, VALUED_1:def 4;
then A6: Z c= dom (cos * ((id Z) ^)) by XBOOLE_1:18;
then A7: cos * ((id Z) ^) is_differentiable_on Z by A1, Th6;
Z c= dom g by A5, XBOOLE_1:18;
then A8: g is_differentiable_on Z by A4, FDIFF_1:9;
A9: for x being Real st x in Z holds
(g `| Z) . x = 2 * x

proof

let x be Real; :: thesis: ( x in Z implies (g `| Z) . x = 2 * x )
assume A10: x in Z ; :: thesis: (g `| Z) . x = 2 * x
diff (g,x) = 2 * (x #Z (2 - 1)) by A3, TAYLOR_1:2
.= 2 * x by PREPOWER:35 ;
hence (g `| Z) . x = 2 * x by A8, A10, FDIFF_1:def 7; :: thesis: verum

end;

for y being object st y in Z holds
y in dom ((id Z) ^) by A6, FUNCT_1:11;
then A11: Z c= dom ((id Z) ^) ;

now :: thesis: for x being Real st x in Z holds
((g (#) (cos * ((id Z) ^))) `| Z) . x = ((2 * x) * (cos . (1 / x))) + (sin . (1 / x))

let x be Real; :: thesis: ( x in Z implies ((g (#) (cos * ((id Z) ^))) `| Z) . x = ((2 * x) * (cos . (1 / x))) + (sin . (1 / x)) )
assume A12: x in Z ; :: thesis: ((g (#) (cos * ((id Z) ^))) `| Z) . x = ((2 * x) * (cos . (1 / x))) + (sin . (1 / x))
then ((g (#) (cos * ((id Z) ^))) `| Z) . x = (((cos * ((id Z) ^)) . x) * (diff (g,x))) + ((g . x) * (diff ((cos * ((id Z) ^)),x))) by A2, A7, A8, FDIFF_1:21
.= (((cos * ((id Z) ^)) . x) * ((g `| Z) . x)) + ((g . x) * (diff ((cos * ((id Z) ^)),x))) by A8, A12, FDIFF_1:def 7
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + ((g . x) * (diff ((cos * ((id Z) ^)),x))) by A9, A12
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + ((x #Z 2) * (diff ((cos * ((id Z) ^)),x))) by A3, TAYLOR_1:def 1
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + ((x #Z 2) * (((cos * ((id Z) ^)) `| Z) . x)) by A7, A12, FDIFF_1:def 7
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + ((x #Z (1 + 1)) * ((1 / (x ^2)) * (sin . (1 / x)))) by A1, A6, A12, Th6
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + (((x #Z 1) * (x #Z 1)) * ((1 / (x ^2)) * (sin . (1 / x)))) by TAYLOR_1:1
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + ((x * (x #Z 1)) * ((1 / (x ^2)) * (sin . (1 / x)))) by PREPOWER:35
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + ((x * x) * (((1 * 1) / (x * x)) * (sin . (1 / x)))) by PREPOWER:35
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + ((x * x) * (((1 / x) * (1 / x)) * (sin . (1 / x)))) by XCMPLX_1:102
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + (((x * (1 / x)) * (x * (1 / x))) * (sin . (1 / x)))
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + (((x * (1 / x)) * 1) * (sin . (1 / x))) by A1, A12, XCMPLX_1:106
.= (((cos * ((id Z) ^)) . x) * (2 * x)) + ((1 * 1) * (sin . (1 / x))) by A1, A12, XCMPLX_1:106
.= ((cos . (((id Z) ^) . x)) * (2 * x)) + (sin . (1 / x)) by A6, A12, FUNCT_1:12
.= ((cos . (((id Z) . x) ")) * (2 * x)) + (sin . (1 / x)) by A11, A12, RFUNCT_1:def 2
.= ((cos . (1 * (x "))) * (2 * x)) + (sin . (1 / x)) by A12, FUNCT_1:18
.= ((2 * x) * (cos . (1 / x))) + (sin . (1 / x)) by XCMPLX_0:def 9 ;
hence ((g (#) (cos * ((id Z) ^))) `| Z) . x = ((2 * x) * (cos . (1 / x))) + (sin . (1 / x)) ; :: thesis: verum

end;

hence ( g (#) (cos * ((id Z) ^)) is_differentiable_on Z & ( for x being Real st x in Z holds
((g (#) (cos * ((id Z) ^))) `| Z) . x = ((2 * x) * (cos . (1 / x))) + (sin . (1 / x)) ) ) by A2, A7, A8, FDIFF_1:21; :: thesis: verum