
theorem Th1372:
Sum digits(4925,10) = 20
proof
  thus Sum digits(4925,10) = Sum <%5,2,9%>+Sum <%4%> by Th1371,AFINSQ_2:55
  .= Sum <%5,2%> + Sum <%9%> + Sum <%4%> by AFINSQ_2:55
  .= (5 + 2) + Sum <%9%> + Sum <%4%> by AFINSQ_2:54
  .= (5 + 2 + 9) + Sum <%4%> by AFINSQ_2:53
  .= 16 + 4 by AFINSQ_2:53
  .= 20;
end;
