the minimum reactionary distance from an unarmed attack is

What is the difference between minimum and infimum? I have a great confusion about this. I'm searching for some symbol representing minimum that is commonly used in math equations. What is the difference between the minimum value and the lower bound of a function? To me, it seems that they are the same. In short, I want to know the minimum numbers of triangles for triangulations of well-known sufaces (torus, projective plane, and Klein bottle), or the way to calculate them. How can I find maximum and minimum modulus of a complex number?

How do I estimate the minimum and the maximum values of normally ... There's a few nice ways to do this but I focus on the technique of (1) make the minimum eigenvalue 0, i.e. all associated eigenvectors for the minimum eigenvalue $\in \ker A$.