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Re: Adding Vectors -- Newbie help please
*To*: mathgroup at smc.vnet.net
*Subject*: [mg52052] Re: Adding Vectors -- Newbie help please
*From*: Paul Abbott <paul at physics.uwa.edu.au>
*Date*: Tue, 9 Nov 2004 01:36:36 -0500 (EST)
*Organization*: The University of Western Australia
*References*: <cmfc9b$7k3$1@smc.vnet.net> <cmhut5$ppb$1@smc.vnet.net> <cmklrk$jm3$1@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
In article <cmklrk$jm3$1 at smc.vnet.net>, motz art <music at heart.com>
wrote:
> Ok; but I was hoping that there is a simpler way than the
> following method to add two ac voltage vectors (for example):
>
> (220V, 225 degrees)
> (100V, 16 degrees)
>
> Clear[r, x, y, Theta, rect, polar]
>
> (* Input vectors here *)
> v1 := {220, 225};
> v2 := {100, 16};
No need for := here. Also, include Degree:
v1 = {220, 225 Degree};
v2 = {100, 16 Degree}
> rect[r_,Theta_] := { r Cos[Theta Pi/180] , r Sin[Theta Pi/180]}
> polar[x_, y_] := {Sqrt[x^2 + y^2], ArcTan[x, y]180/Pi}
Modify these to
PolarToRectangular[{r_,Theta_}] := {r Cos[Theta] , r Sin[Theta]}
RectangularToPolar[{x_, y_}] := {Sqrt[x^2 + y^2], ArcTan[x, y]/Degree}
Alternatively,
PolarToRectangular[{r_,Theta_}] := r Exp[I Theta]
RectangularToPolar[z_] := {Abs[z], Arg[z]/Degree}
> r1:= rect[v1[[1]], v1[[2]] ] // N;
> r2:= rect[v2[[1]], v2[[2]] ] // N;
> rt := p1 + p2
>
> polar[rt[[1]], rt[[2]]] // N
The addition of vectors (phasors) now reads
RectangularToPolar[PolarToRectangular[v1]+PolarToRectangular[v2] // N]
which I find a little less cumbersome.
> This just seems so cumbersome, especially when compared to a
> scientific calculator.
You could, of course, write a palette or program buttons to do this,
just like a scientific calculator.
Cheers,
Paul
> On Sat, 6 Nov 2004 07:36:05 +0000 (UTC), David Bailey
> <dave at Remove_Thisdbailey.co.uk> wrote:
>
> >motz art wrote:
> >> Mathematica v5: How can I input vectors in polar form and
> >> rectangular form?
> >>
> >> Example:
> >>
> >> a:= (r1, theta1) + (r2, theta2) Polar form.
> >>
> >> b:= (re1 , j* im1) + (re2, j*im2) Rectangular form
> >>
> >> I know this should be pretty basic, but I haven't found examples
> >> of this kind of input.
> >>
> >> I would guess it would be something like:
> >>
> >> Polar[magnitude, phase]
> >> Rectangular[Real, Imaginary]
> >>
> >> but, apparently not. (This is for electronics engineering.)
> >>
> >> Thanks for any help.
> >>
> >>
> >>
> >>
> >>
> >You can easily write a function to convert from polar to coordinate form:
> >
> >FromPolar[r_, theta_] := {r Cos[theta], r Sin[theta]}
> >
> >Note that this assumes your angles are measured in radians. Once all
> >your vectors are in coordinate form you can add/subtract then directly:
> >
> >{1,2}+(3,4}
> >
> >produces
> >
> >{4,6}
> >
> >Regards,
> >
> >David Bailey
>
--
Paul Abbott Phone: +61 8 6488 2734
School of Physics, M013 Fax: +61 8 6488 1014
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