28. (a) Prove the identity: sec A − 1 sec A + 1 = 1 − cos A 1 + cos A   29. (b) The mid point of the line segment joining (2a, 4) and (−2, 2b) is (1, 2a + 1). Find the values of a and b. (Type in the answers separated by commas. Leave no spaces around the commas.)   30. (c) In the given figure, if ∠ACE = 43° and ∠CAF = 62° find the values of a, b and c. (Type in the answers separated by commas. Leave no spaces around the commas.)