How to find if an aircraft is inside an airspace using latitude and longitude?
It is just a well-known computational geometry problem called PIP (point-in-polygon). I assume that the airspace is pretty small, and we can consider its boundaries as lines (not curves) in a plane.

Firstly convert latitude and longitude minutes and seconds to fractions. Then use any of PIP algorithms (or libraries, if you do it in any programming language).

For more information check: wiki or this link.

You can also use WolframAlpha for that, or any programming language with a specific library (for example, OpenCV does it very well in C++ or python).