set polar
set border 0 lt 0
unset tics
set rtics 0.2 format ""
set grid polar
set term pngcairo enh font "Arial,10" size 480,480
set out "polar_points.png"
set size ratio -1
set rrange [0:1]
set samp 200
plot cos(2.5*t)**2 w points pt 7 ps 0.5