Question 1159866
Determine the area of the right triangle with vertices R(4,4), S(-2,-2), and T(10,-2).
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Another method:
<pre>
   R   S   T   R
x  4  -2  10   4
y  4  -2  -2   4
</pre>
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Add the diagonal products starting at the upper left:
--> 4*(-2) + -2*-2 + 10*4 = -8 + 4 + 40 = 36
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Add the diagonal products starting at the lower left:
--> 4*-2 + -2*10 + -2*4 = -8 -20 - 8 = -36
The difference is 72.
The area is 1/2 that, = 36 sq units.
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Might be the "hard way" for a triangle, but it works for any plane figure, with any # of sides.
The points must be entered in order around the figure is the only restriction.