Answer:
The brace is
ft ≅ 12.806 ft long
Explanation:
The length of the diagonal of a rectangle can be found using this rule
, where
∵ The gate has shaped a rectangle
∵ Its length = 10 ft
∵ Its width = 8 ft
∴ l = 10 and w = 8
∵ The brace is the diagonal
→ By using the rule above
∴

∴ The length of the brace =
≅ 12.806 ft
∴ The brace is
≅ 12.806 ft long