<PRE><B>Question 1063014</B>
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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&lt;pre&gt;
A    B    C    D    A
2    4   -1   -3    2    --- x values
-1   3    2   -2   -1    --- y values
&lt;/pre&gt;
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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