Actually Cristopher, you are a little off. Notice that it's Vi-Vj-(Vj-Vk).
Distributing the minus into the parenthesis yields Vi-2Vj+Vk.
Now the vector sub, add, and length can be used, as J.Lee Dixon indicated.
Paraskevas
--- Christopher Kim <[EMAIL PROTECTED]> wrote:
> When you do it by hand, due to communitive property of vector matrix, the
> equation
>
> | ( Vi - Vj ) - ( Vj - Vk ) |
>
> will become
>
> | ( Vi + Vk ) |
>
> since you multiply the -1 to the right side and add them.
>
> and with using the Math.sqrt((Xi+Xk)^2+(Yi+Yk)^2)
> will give you the amplitude of the vector.
>
> ---
> Chris Kim
> Iowa State University
>
> >From: Tien Tran Thuong <[EMAIL PROTECTED]>
> >Reply-To: Discussion list for Java 3D API <[EMAIL PROTECTED]>
> >To: [EMAIL PROTECTED]
> >Subject: Re: [JAVA3D]
> >Date: Tue, 6 Feb 2001 14:36:12 +0100
> >
> >thank you for you reply
> >
> >there are three point: i, j and k.
> >Vi = (Xi, Yi), Vj = (Xj, Yj) and Vk = (Xk, Yk) are the coordinates of
> >i,j,k
> >I'd like to know how to calculate:
> >| ( Vi - Vj ) - ( Vj - Vk ) |
> >
> >it's knew that : | Vi - Vj | = Math.sqrt( (Xi-Xj)*(Xi-Xj) -
> >(Yi-Yj)*(Yi-Yj) )
> >
> >thank you
> >
> > > Hi Tien,
> > >
> > > Are you referring that "Vi-1" is "V sub i minus1" and "Vi+1" is "V
> sub i
> > > plus 1"?
> > >
> > > | ( Vi-1 - Vi ) - ( Vi - Vi+1 ) |
> > >
> > > ----
> > > Chris Kim
> > > Iowa State University
> > >
> > > >From: Robert Pies <[EMAIL PROTECTED]>
> > > >Reply-To: Discussion list for Java 3D API
> ><[EMAIL PROTECTED]>
> > > >To: [EMAIL PROTECTED]
> > > >Subject: Re: [JAVA3D]
> > > >Date: Tue, 6 Feb 2001 13:30:19 +0100
> > > >
> > > >Hi Tien,
> > > >
> > > >I can't make sense out of your expression for at least 2 reasons:
> > > >
> > > >a) if Vi is a vector (xi,yi), the term 'Vi-1' doesn't make sense
> > > >b) 'Vi-Vi' would be (0,0), so all the Vi's in your expression cancel
> > > > out...
> > > >
> > > >Maybe the '-' in your expression is really a '*' denoting the
> > > >(inner) vector-product?
> > > >
> > > >If you tell the mailinglist what you're trying to do, maybe some-
> > > >one can make sense of it and help you.
> > > >
> > > >cheers,
> > > >
> > > >Robert.
> > > >
> > > >
> > > >
> > > > > Tien Tran Thuong wrote:
> > > > >
> > > > > Hello,
> > > > >
> > > > > Could anyone show me please how to calculate the expression below
> :
> > > > >
> > > > > | ( Vi-1 - Vi ) - ( Vi - Vi+1 ) |
> > > > >
> > > > > Where Vi = (xi,yi) is coordinate of the i-th vertex.
> > > > >
> > > > > Thank you in advance
> > > >
> > > >--
> > > >
> > > >---------------------------------------------------
> > > >Robert Pies
> > > >Ludwigstr. 58
> > > >04315 Leipzig
> > > >Germany
> > > >+49-341-6888217 (phone&fax)
> > > >[EMAIL PROTECTED]
> > > >
> > > >
> > > >--
> > > >
> > > >---------------------------------------------------
> > > >Robert Pies
> > > >Ludwigstr. 58
> > > >04315 Leipzig
> > > >Germany
> > > >+49-341-6888217 (phone&fax)
> > > >[EMAIL PROTECTED]
> > > >
> > >
> >
>
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