defpred S₁[ object ] means $1 is LinearOperator of X,Y;
consider IT being set such that
A1: for x being object holds
( x in IT iff ( x in Funcs ( the carrier of X, the carrier of Y) & S₁[x] ) ) from XBOOLE_0:sch 1();
take IT ; :: thesis: ( IT is Subset of (ComplexVectSpace ( the carrier of X,Y)) & ( for x being set holds
( x in IT iff x is LinearOperator of X,Y ) ) )
for x being object st x in IT holds
x in Funcs ( the carrier of X, the carrier of Y) by A1;
hence IT is Subset of (ComplexVectSpace ( the carrier of X,Y)) by TARSKI:def 3; :: thesis: for x being set holds
( x in IT iff x is LinearOperator of X,Y )
let x be set ; :: thesis: ( x in IT iff x is LinearOperator of X,Y )
thus ( x in IT implies x is LinearOperator of X,Y ) by A1; :: thesis: ( x is LinearOperator of X,Y implies x in IT )
assume A2: x is LinearOperator of X,Y ; :: thesis: x in IT
then x in Funcs ( the carrier of X, the carrier of Y) by FUNCT_2:8;
hence x in IT by A1, A2; :: thesis: verum