I'm investigating about the best way to know what coordinates are around an specific coordinate. I mean: If am in the coordinate:
@29.817178,-95.4012915
How I can know if the coordinate: @30.00121, -93.13213 has 50km (or less) of my actual position?
Since you're dealing with latitude and longitude, you need to calculate the great circle distance between your two points.
The formula is a bit detailed so I won't reproduce it here, but it's explained in the above linked Wikipedia article.