
theorem Th36:
for X be non empty set, f,g be PartFunc of X,ExtREAL st f = -g holds g = -f
proof
   let X be non empty set, f,g be PartFunc of X,ExtREAL;
   assume f = -g; then
   f = (-1)(#)g by MESFUNC2:9; then
   -f = (-1)(#)((-1)(#)g) by MESFUNC2:9; then
   -f = ((-1)*(-1))(#)g by Th35;
   hence g = -f by MESFUNC2:1;
end;
