I want to find a closed form for the average value of $\cos\{t-\cos t\}$ where $\{n\}$ denotes the fractional part of $n$. I do not have experience finding an average value over an infinite domain but I assume it would be something like this: $$\lim_{x\to\infty}\frac{\int_{0}^{x}\cos\{t-\cos t\}dt}{x}$$ I am not sure if the limit converges. Here is what I have from Desmos:
$$\begin{array}{|c|c|} \hline x & \frac{\int_{0}^{x}\cos\{t-\cos t\}dt}{x} \\\hline 10 & 0.829164368874\\\hline 10*10^3 & 0.834299716027\\\hline 10*10^6 & 0.859423358961\\\hline 10*10^9 & 0.840428861971\\\hline 10*10^{14} & 0.826897135363\\\hline 10*10^{15} & 0.958730802913\\\hline 10*10^{16} & 0.995401790748\\\hline 10*10^{26} & 0.999999999999\\\hline 10*10^{27} & 1\\\hline \end{array}$$
As you can see, the limit appears to oscillate which makes sense after looking at the graph. When it gets to 10$^{\text{15}}$, it suddenly jumps up and begins to approach 1. My intuition tells me this is probably a bug because I am using such high numbers. I tried to solve it by hand but failed to figure out how to convert it to a summation.
I have a few ideas to what it converges to (assuming it does and is not 1) but they are basically wild guesses. $$\cos(\cos(1))\approx 0.857553215846$$ $$\frac{\pi^2}{12}\approx 0.822467033424$$ All help is appreciated :)
(x+1 == x)
may evaluate true. $\endgroup$