5. Solve the inequality log<log4.
6. Solve the inequality sin 2r > 2sin r (0 < x < 2r).
7. Let a = 1, 2, 3, b = 3, 2, 1, c = 5, 4, 3. Find the value of t such that a + tb is parallel to c.
8. Let O(0, 0) and A(3, 1). Let A' be the symmetric point of A with respect to the line y = 2r. Calculate the area of the triangle OAA'.