let FMT be non empty FMT_Space_Str ; :: thesis: for x being Element of
for A being Subset of holds
( x in A ^Fodelta iff for W being Subset of st W in U_FMT x holds
( W meets A & W meets A ` ) )

let x be Element of ; :: thesis: for A being Subset of holds
( x in A ^Fodelta iff for W being Subset of st W in U_FMT x holds
( W meets A & W meets A ` ) )

let A be Subset of ; :: thesis: ( x in A ^Fodelta iff for W being Subset of st W in U_FMT x holds
( W meets A & W meets A ` ) )

thus ( x in A ^Fodelta implies for W being Subset of st W in U_FMT x holds
( W meets A & W meets A ` ) ) :: thesis: ( ( for W being Subset of st W in U_FMT x holds
( W meets A & W meets A ` ) ) implies x in A ^Fodelta )
proof
assume x in A ^Fodelta ; :: thesis: for W being Subset of st W in U_FMT x holds
( W meets A & W meets A ` )

then ex y being Element of st
( y = x & ( for W being Subset of st W in U_FMT y holds
( W meets A & W meets A ` ) ) ) ;
hence for W being Subset of st W in U_FMT x holds
( W meets A & W meets A ` ) ; :: thesis: verum
end;
assume for W being Subset of st W in U_FMT x holds
( W meets A & W meets A ` ) ; :: thesis: x in A ^Fodelta
hence x in A ^Fodelta ; :: thesis: verum