(4) (10 pages) Find an interval of length 7r that contains a root of the equation a: |cos(x)| = 1/2. (6) (Extra credit, 5 points) Suppose f($) is continuous at :17 = 3:0 and assume that f(:z:0) > 0. Prove that there exists an interval (:60 h, 330 + h), where h > 0, in which f (:17) > 0