The angles are the only constraint here that counts. If one of the three interior angles of a supposed triangle is 50 degrees and another is 80 degrees, then the third angle must be 50 degrees. Thus, we have a 50-50-80 triangle, which is isosceles though not a right triangle. If 4 feet is a measure of one of the equal sides of a supposed triangle, then obviously the adjacent side also has measure 4 ft.
The set of angles remains the same (50-50-80), but subject to the constraint mentioned above, the measure of any one of the sides has infinitely many possible values, so long as those values are positive.
