Lesson: how to catch a lady by three. Triangle Petrova - the traditional Russian name for the endgame in Russian checkers, given in honor of the famous shashist Alexander Dmitrievich Petrov. With the help of such a technique, catching a lone lady by three ladies controlling the road (the longest diagonal on the board) is achieved. Abroad is called "the method of Montero", "the classical method HISTORY: First published in the Book for Playing Checkers by Pedro Ruizo Montero in 1591; It is known that Montero applied in practice this method of winning six years before the book was published. For the first time in Russia, the method is published in the book Manual for a thorough knowledge of the draft game of 1827, published anonymously by AD Petrov. Ukrainian master A. Kolesnikov pointed out that the winning strategy shown by A. D. Petrov in the ending, where the white ladies a1, c1, c3 and the black lady b8 participate, is given in the book of Montero and, therefore, was borrowed from the Spanish checkers. When at the end of the game one player will have one lead on the big line, and the other three will bring, then you can not catch the three doves. [...] But if a large line is occupied with three good words, then one can catch. Many players still believe that it is impossible to win with three, and if it happens, it is mostly due to the error of the player who has one lead, and that with the careful consideration of each opponent's move, you can avoid losing. But this is completely unfair. On the contrary, I argue (as you can see from the examples presented) that whatever the player is, with 12 moves or less, allowing him to change moves, he will be forced not to lose by an unintentional mistake, but only from the impossibility of avoiding a loss. For this, the following rule should be observed: firstly, after leaving one lead on a large line, two other middle lines: 5-32 [a7-g1] and 1-28 [b8-h2] and put them on cells 23 and 19 [e3 and f4]; Then with the lead that remained on the big line to step on cell 22 or 11 [c3 or f6], through this disgusting urge will be forced to leave line 3-21 [f8-a3] and step on the side cage, from where will have only extreme Lines: 13 - 2 - 20 - 31 - 13 [a5 - d8 - h4 - e1 - a5]; Then one of the two checkers, standing on the middle lines 23 and 19 [e3 or f4], step on the line 3-21 [f8-a3], and make three triangles in such a way that the lead, making the acute angle of the triangle, Was in the heads of the opposite; Then with three moves caught. - A guide to a thorough knowledge of drafts. - St. Petersburg, 1827. - P. 32-38. The name of the method of fishing is given by the characteristic geometric pattern of the key position, also called the Petrov's triangle (see diagram, see other curves of the board here). The first publisher (for Russian drafts) of an important endgame reception called this arrangement the triangle. Another way of winning in this normal ending is known - the "bayonet Gonyaev", found in 1865 by Mikhail Gonyaev (as well as AD Petrov, chess player and chess player). If before the knowledge of the way of catching three ladies of one not on the highway was a sign of a high class player, then now put the triangle Petrov is classified according to the IIth adult category of the shashist. However, computer programs that are effective even for a candidate may not cope with a standard endgame. A brief description of the method of constructing the Petrov triangle.