To solve this problem, we can use the Pythagorean theorem. The Pythagorean theorem states that for a right triangle, the square of the hypotenuse (in this case, the slant height) is equal to the sum of the squares of the other two sides.
Let's denote the length of one side of the square base as "x". We can then form a right triangle using the height, the slant height, and the side length.
Using the Pythagorean theorem, we can write the equation:
x^2 + 321^2 = 436.5^2
Simplifying this equation, we have:
x^2 + 103041 = 190672.25
x^2 = 190672.25 - 103041
x^2 = 87631.25
Taking the square root of both sides to solve for x, we have:
x = β87631.25
x β 296.1
Therefore, the length of the edge of the square base is approximately 296.1 ft, rounded to the nearest tenth.