Re: Newbie: Rotataion2D use problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg66724] Re: Newbie: Rotataion2D use problem*From*: Peter Pein <petsie at dordos.net>*Date*: Sat, 27 May 2006 21:03:49 -0400 (EDT)*References*: <e591hh$35m$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

akil schrieb: > I have some problems using Mathematica's Rotate2D, it doesnot give the results as I want them > > Eample: > > a={10, 30} > b={80., 0.} > c={38.7689, 0.} > theta = -0.24497866312686414` > theta2 = -0.3430239404207034` > Rotate2D[a, theta, test[[1]]] > Rotate2D[%, theta2, test[[2]]] > > this gives: > \!\({2.7134309891835002`, 1.7763568394002505`*^-15}\) > > While the y-value should be 0 instead of 1.7763568394002505`*^-15. > > Anyone know how I can easily fix this, so that I get 0 here instead? > > Explanation of reasoning: I need to rotate points about points so that they have the same values, and sometimes like here there are a couple of rotations about points needed, and I always get these weird values, but I reeally need them to be 0 for further research purposes. > > (By the way, thanks to all people that replied to my previous post, still need to decide on which one to use, but the problem got a bit harder there, by some complications that are now involved, something to do with clockwise order of found points.) > > Akil > Hi Akil, try Chop (see http://documents.wolfram.com/mathematica/functions/Chop) or use exact numbers. hth, Peter