After summarizing the definition of similar triangles and various similarity shortcuts, we delve into this problem by drawing a diagram, being careful to match up our corresponding vertices.  The vigilant among you will note that even I struggled to do that with a competent level of proficiency judging by the existence of two N's in my diagram.  Fortunately, I spot the problem before the conclusion of the video, thereby saving my family and a clan of my ancestors from a slow death by embarrassment.  Duration: 11:43