let D be non empty set ; :: thesis: for d1, d2, d3 being Element of D holds <*d1,d2,d3*> in 3 -tuples_on D
let d1, d2, d3 be Element of D; :: thesis: <*d1,d2,d3*> in 3 -tuples_on D
<*d1,d2,d3*> in { <*c1,c2,c3*> where c1, c2, c3 is Element of D : verum } ;
hence <*d1,d2,d3*> in 3 -tuples_on D by Th100; :: thesis: verum