[math-fun] what is this function sqrt(x-2+5/x)?
Last nite, taking up a chase I abandoned before he was born, Julian derived "the q-cosine of pi/5" (p 16, line 4) according to my version of q-trig<http://gosper.org/symsac.pdf>. (He also got the much messier sine. Unfortunately sin^2+cos^2 /=1 in q-land.) From these I found the missing 4th eqn on p 15. To save you some indigestion, my q-sine and q-cosine are just tweaks of theta functions, and the Pi_q are theta constants, q-analogs of Wallis's product. Both of these new formulae contain the same mysterious sqrt(x-2+5/x) that stymied me when it showed up in the quintuple formula. People still ask whether it's a misprint. Note that by line 8 of p15, the sqrt (in this q-trig context) can be replaced by a rational function if we introduce a Pi_q^10. Does this ring any bells? --rwg
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Bill Gosper