Question

Mathematica的NDsolve指令怎么用？

m = 1; n = 1; a1 = 1; a2 = 1; r = 1;
sol = NDSolve[{x1'[
N] == -3*
x1[N]*(1 + m*x1[N]^2 - n*x2[N]^2 -
r*(1 + m*x1[N]^2 - m*y1[N]^2 - n*x2[N]^2 - n*y2[N]^2)/2) -
Sqrt[6]*a1*y1[N]^2/2,
y1'[N] ==
3*y1[N]*(-m*x1[N]^2 + n*x2[N]^2 +
r*(1 + m*x1[N]^2 - m*y1[N]^2 - n*x2[N]^2 - n*y2[N]^2)/2 -
a1*Sqrt[6]*x1[N]/6),
x2'[N] == -3*
x2[N]*(1 + m*x1[N]^2 - n*x2[N]^2 -
r*(1 + m*x1[N]^2 - m*y1[N]^2 - n*x2[N]^2 - n*y2[N]^2)/2) +
Sqrt[6]*a2*y2[N]^2/2,
y2'[N] ==
3*y2[N]*(-m*x1[N]^2 + n*x2[N]^2 +
r*(1 + m*x1[N]^2 - m*y1[N]^2 - n*x2[N]^2 - n*y2[N]^2)/2 -
a2*Sqrt[6]*x2[N]/6), x1[0] == 0.05, y1[0] == 0.75,
x2[0] == 0.05, y2[0] == 0, 75}, {x1[N], y1[N], x2[N], y2[N]}, {N,
0, 10}]
t = 1; Evaluate[{x1[t], y1[t], x2[t], y2[t]} /. sol]
我想计算数值解，但总是不行。
mathematica提示说：ReplaceAll::reps: {<<1>>} is neither a list of replacement rules nor a valid dispatch table, and so cannot be used for replacing. >>
____________________
t = 1; Evaluate[{x1[t], y1[t], x2[t], y2[t]} /. sol],这个是用来显示解的值的。请指教。
我已经知道问题的答案在哪了。各位就不用再费劲了～至于悬赏分，就看情况吧。

Answer 1

太乱了，

Answer 2

学问社区——mathematica小组里面好多类似的问题，你可以去看看，挺不错的

Answer 3

Please replace the ',' to '.'. OK?