Thales Theorem in a triangle (The line L parallel to the side BCcuts side AB into the segments AP and PB, side AC into AQ and QC,and |AP|/|PB|=|AQ|/|QC|)
if A,B,C,P,Q are as in the figure above, so that|AP|/|PB|=|AQ|/|QC|, show that this equation is equivalent to|AP|/|AB|=|AQ|/|AC|
