Let x =. Then = = . Then the original equation is equivalent to = 13, or 5x - 13 = . (1) To solve (1), square both sides. You will get = 144*(1-x^2), 25x^2 - 130x + 169 = 144 - 144x^2, 25x^2 + 144x^2 - 130x + 169 - 144 = 0, 169x^2 - 130x + 25 = 0, = 0, ----> 13x - 5 = 0 ----> 13x = 5 ----> x = . Thus you get = . Then = = = = = . Now = = = .