Divide a Circle (String Art)

A B Cron
Many students want to divide a circle for string art. For a semicircle:
Two sliders: n is an interger slider 1...30 r is a real value for a radius of a circle 0...10 by 0.1 curve01 = Sequence[Curve[radius cos(t), radius sin(t), t, i, i + 2π / n], i, 0, 2π - π / n, π / n] points = Sequence[(radius cos(i), radius sin(i)), i, 0, 2π, π / n]