add comments to the process of solution of equations of the form trig(ax + b) = m
added comments to the solution process of trigonometric equations reducible to algebraic eqs
added log(x, b), added comments to solution process of logarithmic and exponential equations
Merge pull request #3 from mkotov/trig-1

added comments to the process of solution of equations of the form trig(ax+b) = m