Thread: area of quadrilateral
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Old June 14th, 2008, 05:43 AM
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Originally Posted by mr fantastic View Post
When t = 1, A = 1. But your answer gives A = 0 ......
A = \frac{1}{2} \, |(x_1 y_2 - x_2 y_1) + (x_2 y_3 - x_3 y_2) + (x_3 y_4 - x_4 y_3) + (x_4 y_1 - x_1 y_4)|

where the order of the points is such that 1 connects to 2 connects to 3 connects to 4 connects to 1.

So your answer is wrong because you have the order of the points wrong in the formula you used ......

You should get A = \frac{1}{2} \left( \frac{2 t^4}{1 + t^4} + \frac{2}{1 + t^4}\right) = 1, as expected from the special case I considered in my earlier reply.
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