这是二分法求非线性方程的根的程序，即若f(x)=0在[a,b]内有唯一实根且f(a)f(b)<0，求其根的程序。-This is the root of nonlinear equations dichotomy of program, that is, if f (x) = 0 in [a, b] there are the only real roots and f (a) f (b) < 0, find its root procedure.