Show, how given a distance r, one can construct a regular pentagon, whose circumradius is r, using only ruler and compass...

Note 1: The ruler doesn't have any marks, so it's no good for measuring. It's only good for joining 2 points by a line.

Note 2: The circle which circumscribes the polygon, such that the polygon lies entirely within the circle and all of whose vertices lie on the circumference of the circle is the circumcircle of the polygon. The radius of this circle is the circumradius of the circle.

(In reply to re: Solution by Charlie)

Well what I actually meant was that just how we draw a right angle, or 60 degrees or 45 degrees, or 30 degrees, etc. using a compass, just the similar way, we will be measuring or you can say cut off an angle of 72 degrees from a given point. That's whay I left a note Charlie at the end of the comment that I have posted regarding my way of explaining the solution. I knew that something or the other is there which the users might not be able to understand.

Posted by Ravi Raja on 2003-05-16 04:32:39