1..       which of the following functions is not monotonic?

(a) e^x - e^-x           ( b) e^x + e^-x          (c) e^-1/x

                  i know how to find mon. inc or dec but how do we check monotonicity

 

2..          find intervals of monotonicity of the fn  f(x) = 2sinx + cosx   [ 0, 2pi ]

 

              i dont how to find the intervals-- do u do it with graphs?