History of 2015-02-28 Math examples in TeX, part I

10:42 UTC Revision 1 . . . . Marcin BorkowskiI’m currently coauthoring an introductory book on LaTeX. (Yes, yet another one. But apparently there are not that many of them in Polish!) Of course, one of the must-haves is a chapter on typesetting equations. What I wanted, however, is a way to enter them with preservation of the DRY principle.