On 3/21/2013 6:21 AM, WM wrote: > On 21 Mrz., 11:36, YBM <ybm...@nooos.fr.invalid> wrote: >> Le 21.03.2013 07:54, WM a crit : >> >>> Every not necessary line can be removed. Why do you think there should >>> remain unnecessary lines? And if they are needed, which it the first >>> unnecessary line that must remain? >> >> Which is the leg which is necessary in order for a dog to have more >> than two legs? >> > Try to understand set inclusion.
Try to follow your own advice.
Perhaps "proof by reality" will convince you to stop misrepresenting mathematical concepts to your students.