I'm trying to iterate in parametric mode to plot several concentric arcs of circles with the parameter `t` ranging according to a function. I've tried, among others,

```
a=sqrt(2)
plot [-pi/2:pi/2] a*cos(t), a*sin(t)
do for [i=2:10] {
  a=sqrt(2)/i
  set trange [-1./2*acos(-(a**2)/2.):1./2*acos(-(a**2)/2.)]
  replot a*cos(t), a*sin(t)
}

```

what I see is a plot of 10 identical overlapped arcs. I also replaced `replot` with `plot` and only the last arc is retained.

I know "that iteration does not work for plots in parametric mode" (ref. "plot for" in the manual), but this is using a `do for` construct. There must be a way to do this! How?

System: gnuplot Version 5.2 patchlevel 2, windows 10.