I asked WA what is the derivative of $\frac1{\cos((x \bmod \pi/2)-\pi/4))}$ equal to for $x=0$.
A very strange result came out. The exact result is $-\sqrt2 \mathsf{Mod}^{(1,0)}(0,\frac\pi2)$, clicking on Approximate form shows cca. 79.
This number was not what I expected so I clicked on More digits and the number doubled! Now it was about 316! (Note: that's not a factorial)
The result doubles every time I click on More digits, up to cca. 1240.
Link to WA: http://goo.gl/ntJ774
What's the meaning of $\mathsf{Mod}^{(1,0)}$ and is this behaviour correct?