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Problem with finding angles between points in Cartesian plane

• To: mathgroup at smc.vnet.net
• Subject: [mg26060] Problem with finding angles between points in Cartesian plane
• From: "Blitzer" <drek1976 at yahoo.com>
• Date: Wed, 22 Nov 2000 01:55:50 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

I would like to find the angle between 2 points on the Cartesian plane.
However, if I use "ArcTan", it is not able to recognise that points with the
same x-coordinates have an angle of 90 degrees between them. It returns
"Indeterminate".
eg. for a point A (x1, y1) and a point (x1, y2), to find the angle between
them, I use ArcTan[(y2-y1)/(x1-x1)]. However, as the denominator is equal to
"0", this function returns "indeterminate". Is there a way to get around
this problem? Or is there other possible functions which can be used.
I am dealing with a very large array of numbers and thus, it's not possible
to check the coordinates individually.

Would be grateful for any help rendered. Thanks!

Derek

• Follow-Ups:
  • RE: Problem with finding angles between points in Cartesian plane
    • From: "Higinio Ramos Calle" <higra@gugu.usal.es>
  • Re: Problem with finding angles between points in Cartesian plane
    • From: Carl Woll <carlw@u.washington.edu>