非线性方程是指含有指数和余弦函数等非线性函数的方程，例如， 与线性方程相比，无论是解的存在性，还是求解的计算公式，非线性方程问题逗逼线性问题要复杂的多，对于一般线性方程，既无直接法可用，也无一定章程可寻。(Nonlinear equations is refers to the index and cosine function equation of nonlinear functions, such as, for example, compared with the linear equation, whether the existence of the solution, or the calculation formula of solving nonlinear equation problem to make linear problem is more complicated, for general linear equations, neither direct method is available, also do not have a certain articles of association.)