Question

mathematica微分方程相关问题 急！！！！！

m = (13.6/4)*10^(-3);
r1 = 34*10^(-3);
r2 = 25.5*10^(-3);
l = 78*10^(-3);
B = 0.15;
c1 = 0.05;
u = 17.9*10^(-6);
c = 2;
p = 12.9*10^(-6);
v0 = 3.6*34*2*10^-3;
w0 = 8 Pi*30;

A = 2/3 p Pi B (r1^3 - r2^3) Sqrt[1 + (l/(r1 - r2))^2]

8.50036*10^-10 TextCell[""]

ps = m/(Pi (r1 + r2) Sqrt[l^2 + (r1 - r2)^2] + Pi r2^2)
J = ps Pi (r2^4 + Sqrt[1 + l^2/(r1 - r2)^2] (r1^4 - r2^4))

0.20348

5.66073*10^-6

k = (r1 - r2) 2 Pi c1*(1/4) p (r1^4 - r2^4) Sqrt[1 + l^2/(r1 - r2)^2]

7.26192*10^-14

W = 1*(2.3^c) k (u/((p ((r1 + r2)/2)^2) - 1 u)^c)/J

0.00379608
DSolve[{A w0 x'[t] - 2 m g = 2 m y''[t], -A w0 y'[t] = 2 m x''[t],
y[0] = 0, x[0] = 0, y'[0] = g, x'[0] = v0}, {x, y}, t]
Set::write: Tag Plus in -0.06664+6.40912*10^-7 (x^\[Prime])[t] is Protected.

Set::write: Tag Times in (240 \[Pi]) (-8.50036*10^-10 ) (y^\[Prime])[t] is Protected.

DSolve::deqn: Equation or list of equations expected instead of 0.0068 (y^\[Prime]\[Prime])[t] in the first argument {0.0068 (y^\[Prime]\[Prime])[t],0.0068 (x^\[Prime]\[Prime])[t],0,0,9.8,0.2448}.

DSolve[{0.0068 (y^\[Prime]\[Prime])[t],
0.0068 (x^\[Prime]\[Prime])[t], 0, 0, 9.8, 0.2448}, {x, y}, t]
求更正，求解答
这里是我全部的财富了。。求高手

Answer 1

解决微问题命令 DSolve举例：
y ' = x
命令：DSolve[y'[x] == x, y'[x], x] 按 shift + enter 运行.
结：{{y[x] -> x^2/2 + C[1]}}.
照着例解决自需要问题按 F1 按帮助菜单输入 DSolve 搜索看更例解该命令更细节
刚刚图片没显示：
DSolve[2 x*y''[x] == Sqrt[1 + y'[x]^2], y[x], x]
{{y[x] -> C[2] + 1/3 Sqrt[x] ((-3 + x) Cosh[C[1]] + (3 + x) Sinh[C[1]])}}
y = C2 + 1/3 √x * ((x-3)*Cosh(C1) + (x+3)*Sinh(C1))C1, C2任意数.
Cosh(C1) = (e^(C1) + e^(-C1))/2
Sinh(C1) = (e^(C1) - e^(-C1))/2