For this problem we can see that we have a right triangle given with two equal sides of 25 ft and we need to find the red one side
Since we have a right triangle we can use the Pythagoras theorem given by:

For this case a= b= 25 ft and if we replace we got:

c represent the red side ? if we solve for it we got:

And we got:
![c=\sqrt[]{1250}=\sqrt[2]{25^2\cdot2}=25\sqrt[]{2}](https://img.qammunity.org/2023/formulas/mathematics/high-school/e1q414vv80rjyt0oxvqo751vreasghpajl.png)
![c=25\sqrt[]{2}](https://img.qammunity.org/2023/formulas/mathematics/high-school/1x2h5oqeilczy0e2w8bmk9n7iqr89l764b.png)