I am trying to solve an equation: arccos(Y) = arctan(Y), where Y = 1/x This turns into a quartic equation: x4 - x2 - 1 = 0 It looks simple enough to simplify further; however, I must be having a brain-fart because I can't do it. I'd like to avoid resorting to a numerical solution. Am I overlooking something? Can this equation be simplified further? If so, how? Any help is much appreciated.