it is difficult to know from this side of the screen what is your current level. From my personal experience reverse engineering is mostly learned by doing things: By actually trying to solve a real problem. Usually for me once the problem is solved, I lose interest in the code.
My advice for you is to find a project of larger scale that you want to work on,...
There's a couple of likely possibilities for how the value of Pi is included in the code -
1) It is calculated using trig functions. e.g.
4.0 * atan( 1.0 )
2) It is stored as a floating-point constant. In hexadecimal representation these could be -
0x40490FDB // 32-bit floating point
0x400921FB54442D18 // 64-bit floating point