Prove that if a triangle has an acute angle, then the largest side lies opposite it.

In the problem statement, a triangle is given, one of the angles is obtuse. An obtuse angle is an angle greater than ninety degrees. The sum of all three angles of the triangle is one hundred and eighty degrees, which means that the sum of the other two angles of the triangle will be less than ninety degrees, that is, each of these angles is acute. The larger side lies opposite the larger angle, and since in our task one of the corners is obtuse, the largest side lies opposite it.