Re: Laplace Transforms

On Sat, Mar 27, 2021 at 7:56 PM Matthew Redmayne <[email protected]>
wrote:

> Hello,
>
>
>
> I receive the following error when attempting a simple laplace transform,
> any idea on why it is happening?
>
>
>
>
>
> Regards,
>
>
>
> Matt
>

If you do:

yms t x
f= 10*t^3*cos(15*t);
laplace (f,x)

then octave gives:
ans = (sym)

         ⎛ 4         2        ⎞
      60⋅⎝x  - 1350⋅x  + 50625⎠
  ─────────────────────────────────
            2
  ⎛ 2      ⎞  ⎛ 4        2        ⎞
  ⎝x  + 225⎠ ⋅⎝x  + 450⋅x  + 50625⎠


So Octave symbolic does not like the phase shift!




Maxima gives:
laplace(%10*t^3*cos(15*t+120), t, s);

10*((6*cos(120))/(s^2+225)^2-(24*cos(120)*s^2)/(s^2+225)^3-(24*s*(cos(120)*s-15*sin(120)))/(s^2+225)^3+(48*s^3*(cos(120)*s-15*sin(120)))/(s^2+225)^4)



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