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| Question 429188:  Use coordinates to prove that the diagonals of a rectangle are equal in length.
 Answer by richard1234(7193)
      (Show Source): 
You can put this solution on YOUR website! Since the position of the rectangle is irrelevant, we can assume (without loss of generality, a common math expression) that the vertices of the rectangle are at points (0,0), (a,0), (a,b), and (0,b). The diagonals are determined by the sets of points {(0,0), (a,b)} and {(a,0), (0,b)}. We use the distance formula to find each distance: 
 {(0,0), (a,b)}
 
   
 {(a,0),(0,b)}
 
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 These two distances are equal in length, so we are done.
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