The problem can be observed in the figure below.
To find the missing value "c", follow the steps below.
Step 01: Write the Pythagorean theorem.

Where:
c = hypotenuse.
a and b = legs.
Step 02: Substitute the values in the equation.
a = 30.
b = 45.

Taking the root from both sides:
![\begin{gathered} \sqrt[]{c^2}=\sqrt[]{2925} \\ c=54.08 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/i9ssfi29f65mj5plvba27mefd8f2bthunf.png)
Answer: The diagonal c measures 54.08 feet.