Notta problem my friend.
No missunderstandings here, I knew you were aware of the other method NeoStrider suggested, but were more concerned about a way of doing it with geometry.
Besides, it's by understanding the various methods available that one is able to make a decision on the most appropriate method for the task at hand.
I mean, if we didn't need to learn from experience, then school would be about nothing other than reading - we wouldn't need to 'waste' our time with practical work. It is experience that gives us the knowledge required to make the best decisions.
Anybody can teach, but the thing that sets apart the truly great teachers is that they are prepared to adopt the lessons to suit the student, whereas the standard model is to expect the student to learn what they're being taught, the way it is being taught. Regardless of the suitability of the method to the students.
Note to Neostrider: Sorry I was a little terse mate. No hard feelings intended..