说明： 用改进的欧拉方法求解初值问题,其中一阶微分方程未y f(x,y) 初始条件为x x[0]时,y＝y[0] 输入 f-- (The improved Euler method is used to solve the initial value problem. When the initial condition of the first order differential equation is x x [0], when the first order differential equation is not y f (XG y, the input of y y [0] is f--.)
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