WGS-84 is Spherical Mercator, the projection system used by Google, so the coordinates you have provided are obviously not. Unfortunately for any formula to work you will need to find out the projection that your points are in.
Some more detailed information on projection is available here: http://courses.washington.edu/gis250/lessons/projection/
And a library to convert between common coordinate systems in .net is available at: http://www.doogal.co.uk/dotnetcoords.php.
Would it be possible for you to open the map layer in an GIS program such as: http://www.qgis.org/en/site/ and use the options available to determine the projection of the layer?
Some tips for identifying the coordinate system (written for ARCGIS but the programs are similar): http://resources.arcgis.com/en/help/main/10.1/index.html#//003r00000004000000 https://gis.stackexchange.com/questions/7839/best-practices-for-identifying-the-unknown-coordinate-system-of-a-shapefile