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		The figure shows the triangles ABC and 
		A'B'C' so that AA', BB', CC' meet at a point O. AB and A'B' meet 
		at D, AC and A'C' at E, BC and B'C' at F. Prove that D,E, and F are on a 
		line (collinear points).Note. The triangles ABC and A'B'C' are said to be in perspective, O is 
		called the center of perspective or perspector. Line DEF is called the 
		axis of perspective or perspectrix.
 
 
 
				 
 
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