Question 1:Use the Pythagorean theorem.
If

, then the angle is acute.
If

, then the angle is right.
If

, then the angle is obtuse.






Thus, the angle is acute.
Question 2:Take the square root of the area to get the side length.

That's the side length. Since we have a 45-45-90 right triangle if we divide the square across its diagonal, we just multiply the side length by the square root of 2 in order to get the diagonal length.


Your answer is 20 m. Hope this helps! :)