On your paper, you wrote down a^2+b^2 = c^2 which is the pythagorean theorem
You are on the right track. You'll use this equation. In this case
a = 36
b = 18
c = 43
The value of a and b can be swapped. The value of c is always the longest side.
Let's see if a^2+b^2 = c^2 is true or not
a^2 + b^2 = c^2
36^2 + 18^2 = 43^2
1296 + 324 = 1849
1620 = 1849
The last equation is false so the first equation is false when a = 36, b = 18 and c = 43
We do NOT have a right triangle so we do NOT have a rectangle
Answer: No, the table is not "square" (ie, have right angles at the corners)