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| Question 824253:  Prove that a quadrilateral ABCD with vertices A(-1,4), B(-3,3), C(1,2) and D(3,3) is a parallelogram
 Answer by richwmiller(17219)
      (Show Source): 
You can put this solution on YOUR website! quadrilateral edge lengths
 | (sqrt(5)  |  sqrt(17)  |  sqrt(5)  |  sqrt(17))
 =(2.23607  |  4.12311  |  2.23607  |  4.12311)
 diagonal lengths
 | (2 sqrt(2)  |  6)
 =(2.82843  |  6)
 area | 6
 perimeter | 2 (sqrt(5)+sqrt(17))=12.7183
 interior angles
 | ((180 (pi-tan^(-1)(1/4)-tan^(-1)(1/2)))/pi°  |  (180 (tan^(-1)(1/4)+tan^(-1)(1/2)))/pi°  |  (180 (pi-tan^(-1)(1/4)-tan^(-1)(1/2)))/pi°  |  (180 (tan^(-1)(1/4)+tan^(-1)(1/2)))/pi°)=
 (2.43297 radians  |  0.708626 radians  |  2.43297 radians  |  0.708626 radians)
 interior angle sum | 360° = 2 pi rad
 exterior angle sum | 1080° = 6 pi rad
 
 | (-1, 4) | (-3, 3) | (1, 2) | (3, 3)
 (-1, 4) | 0 | sqrt(5)=2.23607 | 2 sqrt(2)~~2.82843 | sqrt(17)~~4.12311
 (-3, 3) | sqrt(5)~~2.23607 | 0 | sqrt(17)~~4.12311 | 6
 (1, 2) | 2 sqrt(2)~~2.82843 | sqrt(17)~~4.12311 | 0 | sqrt(5)~~2.23607
 (3, 3) | sqrt(17)~~4.12311 | 6 | sqrt(5)~~2.23607 | 0
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