Let gamma be a circle with center O and P a point outside gamma.

Construct a tangent line to gamma through point P using a straightedge only.

Prove the construction.

I have a circle centre O on a line PQ. 

I lay my straight edge from point P to the edge of the circumference of circle γ and draw the line.

Done!

But!   But!  But I did choose the tangent point, where the straight edge touched the circumference!
...
Huh?  Yeah, sure I did it visual, what do you expect?


 See my next comment.  I puzzled about this and this did seem to be the only way to go

Edited on March 15, 2008, 7:54 am

Posted by brianjn on 2008-03-15 07:53:03