let x, y, c be object ; ( [<*x,y*>,'&'] in InnerVertices (MajorityStr (x,y,c)) & [<*y,c*>,'&'] in InnerVertices (MajorityStr (x,y,c)) & [<*c,x*>,'&'] in InnerVertices (MajorityStr (x,y,c)) )
[<*x,y*>,'&'] in InnerVertices (1GateCircStr (<*x,y*>,'&'))
by Th47;
then
[<*x,y*>,'&'] in InnerVertices ((1GateCircStr (<*x,y*>,'&')) +* (1GateCircStr (<*y,c*>,'&')))
by Th21;
then A1:
[<*x,y*>,'&'] in InnerVertices (MajorityIStr (x,y,c))
by Th21;
[<*y,c*>,'&'] in InnerVertices (1GateCircStr (<*y,c*>,'&'))
by Th47;
then
[<*y,c*>,'&'] in InnerVertices ((1GateCircStr (<*x,y*>,'&')) +* (1GateCircStr (<*y,c*>,'&')))
by Th21;
then A2:
[<*y,c*>,'&'] in InnerVertices (MajorityIStr (x,y,c))
by Th21;
[<*c,x*>,'&'] in InnerVertices (1GateCircStr (<*c,x*>,'&'))
by Th47;
then
[<*c,x*>,'&'] in InnerVertices (MajorityIStr (x,y,c))
by Th21;
hence
( [<*x,y*>,'&'] in InnerVertices (MajorityStr (x,y,c)) & [<*y,c*>,'&'] in InnerVertices (MajorityStr (x,y,c)) & [<*c,x*>,'&'] in InnerVertices (MajorityStr (x,y,c)) )
by A1, A2, Th21; verum