In this video, the methodology for solving ordinary differential equations with Dirichlet and mixed boundary conditions using Finite Difference Method has been explained. Programming is done in SCILAB.
n = no of divisions between the boundary. i.e. from 0 to π/2. The more you increase the division, the more you get the accurate results. So, it is not necessary to take n=6, you can take any, for instance say n=10 or 15 or 19 etc. by increasing it you will get the more accurate result.