Answer
The length of the hypotenuse is 35 feet.
Explanation
This is the formula to find the hypotenuse.
![l^(2) + l^(2) = h^(2)](https://img.qammunity.org/2021/formulas/mathematics/college/2gwpoext6211qphdt8y47egp7xiwmdeucm.png)
One leg is 21 feet. The other is 28 feet. Now insert those into the formula.
![21^(2) + 28^(2) = h^(2)](https://img.qammunity.org/2021/formulas/mathematics/college/79ezomrsfqozapu32kqulb257jjxnaqnds.png)
![h^(2)=1225](https://img.qammunity.org/2021/formulas/mathematics/college/nwp1cjz9ky7ko259xcpriui6vxpkti5apk.png)
Now to find what h is you should find the square root of 1225.
![√(1225) =35](https://img.qammunity.org/2021/formulas/mathematics/college/51wrmfqxow5tnwr24wp2ydi417a88yp0xs.png)
So the length of the hypotenuse is 35 feet.