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Re: Calculate the included angle between two vectors [message #65976 is a reply to message #65972]

Thu, 09 April 2009 10:41

Chris[6]
Messages: 84
Registered: July 2008

Member

On Apr 9, 5:43 am, Pierre <pierre.villene...@gmail.com> wrote:
> On Apr 9, 7:14 am, "dux...@gmail.com" <dux...@gmail.com> wrote:
>
>> Is there a function which can calculate the included angle between
>> two three-dimensional vectors?
>
>> jdu
>
> Here's a simple solution. Assume v1 and V2 are each three-element
> vectors of any magnitude. Compute the angle in degrees as follows:
>
> angle = acos( transpose(v1)#v2 / sqrt(total(v1^2)) / sqrt(total
> (v2^2)) ) * 180./!pi
>
> Good luck.

There is an issue with this method due to the fact that acos cannot
distinguish between positive and negative angles (cos(-theta) = cos
(theta)).
I have found this website to be very useful for coding geometry type
problems like this one:
http://local.wasp.uwa.edu.au/~pbourke/geometry/

chris

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[Message index]

		Re: Calculate the included angle between two vectors By: jameskuyper on Fri, 10 April 2009 02:47
		Re: Calculate the included angle between two vectors By: duxiyu@gmail.com on Fri, 10 April 2009 02:15
		Re: Calculate the included angle between two vectors By: Chris[6] on Thu, 09 April 2009 10:41
		Re: Calculate the included angle between two vectors By: Pierre V. on Thu, 09 April 2009 08:43

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