Re: vector.SetTheta()

On Thu, Mar 5, 2009 at 15:00, Eduard Avetisyan <dich_at_mail.desy.de> wrote:
>
> Hi Alexander,
>
> On Thu, 5 Mar 2009, Alexander Mann wrote:
>
>> Hi,
>>
>> When I try and use the SetTheta() function
>> (http://root.cern.ch/root/html/TVector3.html) with negative numbers it
>> seems to use the modulus.  This isn't what I want..!
>>
>> It's quite possible I'm missing something here and, if I am, I'd be
>> grateful to anyone who can point it out.
>
> In spherical coordinate system theta can only be positive. The azimuthal
> orientation is then given by phi. If you try to imagine two vectors in 3d,
> you'll see the (smallest) angle between them is always 0..pi.
>

Ok, thanks for that (and to those who replied offlist).

I think what I actually expecting it to do was move phi by pi - but I can see why settheta wouldn't do that... Anyway, the problem is sorted.

Cheers
Alex Received on Thu Mar 05 2009 - 16:36:15 CET