Using Tikz, I can to make the graph of the $f(x) = \cos x$, $f(x) = \sin x$ , buta I can't to make the of $f (x) = \cos | x |$

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    cos(-x) = cos(x)cos(x) = cos(|x|) – Heiko Oberdiek Sep 28 '15 at 21:37

pgfmath has an abs function. That said, cosine being an even function, cos(x) = cos(-x), so there is no difference between the plots of cos(x) and cos(abs(x)).

\addplot[blue,domain=-360:360,samples=400] {cos(abs(x))};
\addplot[red,ultra thick,dashed,domain=-360:360,samples=400] {cos(x)};

enter image description here

  • I was wrong when I wrote cos x (which is a function pair, so the graph of cos |x| is no problem). Actually, I wanted to do was make the graph of f (x) = | sin |x| |, and I thought I'd just ask a simple question (f(x) = sin|x| )and, after suggestions, I would complete the rest. When I wrote, I changed the sine by the cosine. – benedito Sep 28 '15 at 22:04
  • @benedito sin(abs(deg(x))) – user11232 Sep 29 '15 at 1:41

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