Exercise 3 Page 440

1. Premise: If a polygon ABCD is a square, then it is a rectangle.
2. Premise: Polygon ABCD is a rectangle.
3. Conclusion: Polygon ABCD is a square.

The first premise lets us know that if a four sided polygon is a square, then it is also a rectangle. However, notice that this does not imply that every rectangle is a square. The conclusion has an incorrect use of the first premise, so the deductive reasoning is flawed.