How do I find all zeros of a multivariate function , i.e. f(x1,x2,x2,...xn)=0 numerically? I don't know exact analytic form of f , but can numerically compute f at every point on its domain.
Example: Given a matrix A=[i , a; 3+i , 9], I have to find all complex a such that A has an complex eigenvalue with arguement 37 degrees?
Here i is sqrt(-1).