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Re: NDSolvie[]

• To: mathgroup at smc.vnet.net
• Subject: [mg123533] Re: NDSolvie[]
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Sat, 10 Dec 2011 07:29:49 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201112091058.FAA03928@smc.vnet.net>

x'[t]//FullForm

Derivative[1][x][t]


D[x[t],t]//FullForm

Derivative[1][x][t]


soln1 = NDSolve[{
    Derivative[1][x][t] == -y[t] - x[t]^2,
    Derivative[1][y][t] == 2*x[t] - y[t],
    x[0] == y[0] == 1}, {x, y}, {t, 10}];

soln2 = NDSolve[{
    x'[t] == -y[t] - x[t]^2,
    y'[t] == 2*x[t] - y[t],
    x[0] == y[0] == 1}, {x, y}, {t, 10}];

soln3 = NDSolve[{
    D[x[t], t] == -y[t] - x[t]^2,
    D[y[t], t] == 2*x[t] - y[t],
    x[0] == y[0] == 1}, {x, y}, {t, 10}];

soln1 == soln2 == soln3

True


Bob Hanlon

> Z
> Subject: [mg123513] NDSolve[]
> To: mathgroup at smc.vnet.net
>
> For the same equations, why does the first method as following give
> the error but the other one give the desired result?
>
> NDSolve[{Derivative[x[t], t] == -y[t] - x[t]^2,
>  Derivative[y[t], t] == 2*x[t] - y[t], x[0] == y[0] == 1}, =
{x,
>  y}, {t, 10}]
>
> NDSolve[{x'[t] == -y[t] - x[t]^2, y'[t] == 2*x[t] - y[t],
>  x[0] == y[0] == 1}, {x, y}, {t, 10}]
>

• References:
  • [no subject]
    • From: "Steven M. Christensen" <steve@smc.vnet.net>