A student constructed the following four-step argument in an attempt to prove a theorem from known premises.
Step 1 The Pythagorean theorem states that the square on the hypotenuse of any right triangle equals the sum of the
squares on the other two sides.
Step 2 It is possible to construct a right triangle with sides of length 5, 12, and 13 units.
Step 3 132 - 122 +52
Step 4 The equality in Step 3 proves the Pythagorean theorem.
Which step in the argument is logically incorrect?