利用龙格库塔法（等步长，变步长）计算椭圆方程，双曲线方程，抛物线方程等。对各类微分方程进行数值计算。-The use of Runge-Kutta method (such as step, variable step size) calculated elliptic equations, hyperbolic equations, such as parabolic equation. Various types of differential equations for numerical