Chapter 8.4, Problem 4E

In Exercises 3 and 4, determine whether each set is open or closed or neither open nor closed.

4. a. {(x, y) : x² + y² =1}

b. {(x, y) : x² + y² > 1}

c. {(x, y): x² + y² ≤ 1 and y > 0}

d. {(x, y) : y ≥ x²}

e. {(x, y) : y < x²}