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MathGroup Archive 2004

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Re: Re: Adding Vectors -- Newbie help please

  • To: mathgroup at smc.vnet.net
  • Subject: [mg52041] Re: [mg52023] Re: Adding Vectors -- Newbie help please
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Mon, 8 Nov 2004 03:13:24 -0500 (EST)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

Define a function to add polar forms

rect[{r_, theta_}] := 
    Module[{t=theta Degree},r{Cos[t],Sin[t]}];
polar[{x_,y_}] := 
  {Sqrt[x^2+y^2],ArcTan[x,y]/Degree}
addPolar[p__] := polar[Plus@@(rect/@{p})];

v1:={220,225}; v2:={100,16};

addPolar[v1,v2]//N

{141.127,-114.908}

v3={60,30};

addPolar[v1,v2,v3]//N

{98.2845,-94.3623}


Bob Hanlon

> 
> From: motz art <music at heart.com>
To: mathgroup at smc.vnet.net
> Date: 2004/11/07 Sun AM 01:04:10 EST
> To: mathgroup at smc.vnet.net
> Subject: [mg52041] [mg52023] Re: Adding Vectors -- Newbie help please
> 
> 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]
> 
> 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}
> 
> (* Input vectors here *)
> v1 := {220, 225};
> v2 := {100, 16};
> 
> r1:= rect[v1[[1]], v1[[2]] ] // N;
> r2:= rect[v2[[1]], v2[[2]] ] // N;
> rt := p1 + p2
> 
> polar[rt[[1]], rt[[2]]] // N
> 
> This just seems so cumbersome, especially when compared to a
> scientific calculator.
> 
> 
> 
> 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
> 
> 


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