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(This article was first published on <strong><a href="https://xianblog.wordpress.com/2018/09/19/le-monde-puzzle-1066/"> R – Xi'an's Og</a></strong>, and kindly contributed to <a rel="nofollow" href="https://www.r-bloggers.com/">R-bloggers)</a> </div>
<p><strong><a rel="nofollow" href="https://xianblog.files.wordpress.com/2015/10/lemondapari.jpeg" target="_blank"><img src="https://xianblog.files.wordpress.com/2015/10/lemondapari.jpeg?w=450&h=299&fit=456%2C456" data-recalc-dims="1"></a>T</strong>he second <a rel="nofollow" href="https://xianblog.wordpress.com/2011/09/03/le-monde-puzzle-website/" title="Le Monde puzzle [website]" target="_blank">Le Monde mathematical puzzle</a> in the new competition is sheer trigonometry:</p>
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<p><em><a rel="nofollow" href="http://www.affairedelogique.com/" target="_blank"><img width="130" src="https://i2.wp.com/www.affairedelogique.com/backoffice/img/fck/affairedelogique/Bricolle.jpg" height="132"></a>When in the above figures both triangles ABC are isosceles and the brown segments are all of length 25cm, find the angle in A and the value of DC², respectively.<br>
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<p>This could have been solved by R coding the various possible angles of the three segments beyond BC until the isosceles property is met, but it went much faster by pen and paper, leading to an angle of π/9 in the first case and a square of 1250 in the second case.</p>
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