Answer
$442,815.6 \ square \ miles $
Work Step by Step
According to Heron's formula, the area of a triangle with sides $a,b$ and $c$ is given by:
$K=\sqrt{s(s-a)(s-b)(s-c)}$
where $s=\dfrac{a+b+c}{2}$
Therefore, $s=\dfrac{1028+1046+965}{2}= 1519.5$
In order to find the area of the triangle, we will have to substitute the data into Heron's formula.
$K=\sqrt{1519.5(1519.5-1028)(1519.5-1046)(1519.5-965)} \approx 442,815.6 \ square \ miles $