You can solve this problem by using the pythagorean theorem.
[tex] {a }^{2} + {b}^{2} = {c}^{2} [/tex]
Where the a- and b-values represent the sides of the triangle. Since the park is a sqaure, each side is equal. This means that both the a-value and the b-value are the same. Now, you must find the c-value.
145^2 + 145^2 = c^2
21,025 + 21,025 = c^2
42,050 = c^2 *now square root each side of the equation.*
205.06 = c
The length of the diagonal line is 205 meters.