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        		Tangential or Circumscribed Quadrilateral: Diagonal, Altitudes Theorem. The figure shows a tangential or 
		circumscribed quadrilateral ABCD. The diagonals AC and BD meet at E. If 
		h1, h2, h3, and h4 are 
		perpendicular to AB, BC, CD, and AD, respectively, prove 
		that
		 
                
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