Question 1063014: area of the quadrilateral formed by (2,-1),(4,3),(-1,2),(-3,-2)is
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! area of the quadrilateral formed by (2,-1),(4,3),(-1,2),(-3,-2)is
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Label the points A(2,-1), B(4,3), C(-1,2), D(-3,-2)
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A B C D A
2 4 -1 -3 2 --- x values
-1 3 2 -2 -1 --- y values
Add the diagonal products starting at the upper left:
= 2*3 + 4*2 + -1*-2 + -3*-1 = 6 + 8 + 2 + 3 = 19
Add the diagonal products starting at the lower left:
= -1*4 + 3*-1 + 2*-3 + -2*2 = -4 -3 -6 -4 = -19
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The difference = 38
The area = 1/2 the absolute value of the difference
Area = 19 sq units.
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