let X be non empty set ; :: thesis: for S being SigmaField of X
for M being sigma_Measure of S
for f being PartFunc of X,REAL
for k being positive Real st f in Lp_Functions (M,k) holds
abs f in Lp_Functions (M,k)

let S be SigmaField of X; :: thesis: for M being sigma_Measure of S
for f being PartFunc of X,REAL
for k being positive Real st f in Lp_Functions (M,k) holds
abs f in Lp_Functions (M,k)

let M be sigma_Measure of S; :: thesis: for f being PartFunc of X,REAL
for k being positive Real st f in Lp_Functions (M,k) holds
abs f in Lp_Functions (M,k)

let f be PartFunc of X,REAL; :: thesis: for k being positive Real st f in Lp_Functions (M,k) holds
abs f in Lp_Functions (M,k)

let k be positive Real; :: thesis: ( f in Lp_Functions (M,k) implies abs f in Lp_Functions (M,k) )
set W = Lp_Functions (M,k);
assume f in Lp_Functions (M,k) ; :: thesis: abs f in Lp_Functions (M,k)
then consider f1 being PartFunc of X,REAL such that
A1: ( f1 = f & ex Ef1 being Element of S st
( M . (Ef1 `) = 0 & dom f1 = Ef1 & f1 is Ef1 -measurable & (abs f1) to_power k is_integrable_on M ) ) ;
consider Ef being Element of S such that
A2: ( M . (Ef `) = 0 & dom f1 = Ef & f1 is Ef -measurable & (abs f1) to_power k is_integrable_on M ) by A1;
dom (abs f1) = Ef by ;
then Z1: ( M . (Ef `) = 0 & dom (abs f1) = Ef & abs f1 is Ef -measurable & (abs (abs f1)) to_power k is_integrable_on M ) by ;
thus abs f in Lp_Functions (M,k) by A1, Z1; :: thesis: verum