shadein := proc (f, g, a, c) local i, n, loptions; loptions := [args[5 .. 
nargs]]; if not hasoption(loptions,'numpoints','n','loptions') then n := 50 fi
; seq(polygon([[evalf(a[1]+(a[2]-a[1])*i/n), evalf(f(a[1]+(a[2]-a[1])*i/n))],
[evalf(a[1]+(a[2]-a[1])*(i+1)/n), evalf(f(a[1]+(a[2]-a[1])*(i+1)/n))], [evalf(
a[1]+(a[2]-a[1])*(i+1)/n), evalf(g(a[1]+(a[2]-a[1])*(i+1)/n))]],color = c,
style = patchnogrid,op(loptions)),i = 0 .. n-1), seq(polygon([[evalf(a[1]+(a[2
]-a[1])*i/n), evalf(g(a[1]+(a[2]-a[1])*i/n))], [evalf(a[1]+(a[2]-a[1])*(i+1)/n
), evalf(g(a[1]+(a[2]-a[1])*(i+1)/n))], [evalf(a[1]+(a[2]-a[1])*i/n), evalf(f(
a[1]+(a[2]-a[1])*i/n))]],color = c,style = patchnogrid,op(loptions)),i = 0 ..
n-1) end;