from visual import *

eps = 0.1
step = 10

L=[]
Laxis=[]
for t in arange(0,2*pi+eps, eps):
    L.append((cos(t), sin(t)))
    Laxis.append((-sin(t),cos(t)))

curve(pos = L, radius = 0.01, color=color.red)
points(pos = L, radius = 0.1, color = color.white)
for i in arange(len(L)):
    if i % step == 0:
         arrow(pos = L[i], axis = Laxis[i], shaftwidth=0.01, color=color.blue)      #tangent
         arrow(pos = L[i], axis = (Laxis[i][1], -Laxis[i][0]), shaftwidth=0.01, color=color.green)

# tangent = (x,y), normal = (-y, x) or (y, -x)