title: Constexpr Math Functions
body: <p>So noticed from this <a href="http://en.cppreference.com/w/cpp/numeric/math" rel="noreferrer">page</a> that none of the math functions in c++11 seems to make use of constexpr, whereas I believe all of them could be. So that leaves me with two questions, one is why did they choose not to make the functions constexpr. And two for a function like <code>sqrt</code> I could probably write my own constexpr, but something like sin or cos would be trickier so is there a way around it.</p>