9514 1404 393
Answer:
31.41 ft²
Step-by-step explanation:
Heron's formula is useful when you have the three side lengths.
A = √(s(s -a)(s -b)(s -c)) . . . . sides are a, b, c and s = (a+b+c)/2
Using the given side lengths, we have ...
s = (8 +8.4 +13.5)/2 = 29.9/2 = 14.95
A = √(14.95(14.95 -8)(14.95 -8.4)(14.95 -13.5)) = √(14.95×6.95×6.55×1.45)
A = √986.81399375 ≈ 31.41 . . . . square feet