Derive an equation with logarithmec and trigo functions in it

Hi all,

I am trying to derive an equation to compute the lat and lon variables given an x and y coordinates.
I already have the equations we are using in our game to derived the X and Y coordinates from lat and lon. 
Now we want to derive the formula in reverse. the code bellow shows the original formula to retrieve the X and Y given Lat and Lon that we are using. Well, computing for Lon is easy as it just involves transpose and division but cant seem to figure out how to do it for the …