The most interesting and intriguing
  part of math lies in the triangle.
  Let's assume the sides a, b, c; and
  the angle to the charming one θ.
  So tanθ is the most common and acceptable,
  while cot fewer but still reasonable;
  as to sinθ or its reverse,
  perverse, violating the social commandment.
  Violent sec may be inevitable,
  and sly cos is surely not impossible;
  but what is the real answer to the puzzle?
  Maybe it's sinθ．cscθ,
  Or is it sinθ．sinθ+cosθ．cosθ﹖
  Anyway, the dilemma
  is open for imagination.
  Class dismissed. Oh, pardon me --
  I meant the real one.