see, it's simple to analyze.
since, x can't be negative it can't go to 2nd and 3rd quad
because sinx will become negative and log of negative numbers is not defined.
now, as Sinx cannot be greater than 1.
and log(m) is always negative for 0<m<1.
at m=1, log becomes zero.
For more clarification you can ask again and read the properties of log for better understanding.