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HTML + CSS gold circle

"A circle is a square with rounded corners"

a circle

a point

a line

all perfect

draw a straigth line and follow it

A classic:

http://www.videobash.com/video_show/teacher-draws-a-perfect-circle-389305

http://en.wikipedia.org/wiki/Circle#mediaviewer/File:Circle-withsegments.svg

Using the same tools as on paper: A cup to guide for the circle, a pen to guide for the line, smashing the pen to the paper for the point.

Python turtle module

import turtle

def circle(n,x):

angle=360/n

for i in range(n):

turtle.forward(x)

turtle.left(angle)

print circle(360,1)