take [*(+ x1,y1),(+ x2,y2)*] ; :: thesis: ex x1, x2, y1, y2 being Element of REAL st
( x = [*x1,x2*] & y = [*y1,y2*] & [*(+ x1,y1),(+ x2,y2)*] = [*(+ x1,y1),(+ x2,y2)*] )
thus ex x1, x2, y1, y2 being Element of REAL st
( x = [*x1,x2*] & y = [*y1,y2*] & [*(+ x1,y1),(+ x2,y2)*] = [*(+ x1,y1),(+ x2,y2)*] ) by A2, A4; :: thesis: verum