Exercise 4 Page 440

1. Premise: If a polygon ABCD is a square, then it is a rectangle.
2. Premise: Polygon ABCD is not a square.
3. Conclusion: Polygon ABCD is not a rectangle.

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. We cannot conclude if our polygon is a rectangle or not just by knowing if it is or is not a square. Therefore, the deductive reasoning used is flawed.