Re: Problem with finding angles between points in Cartesian plane
- To: mathgroup at smc.vnet.net
- Subject: [mg26090] Re: Problem with finding angles between points in Cartesian plane
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Tue, 28 Nov 2000 01:55:35 -0500 (EST)
- References: <8vfqv9$jif@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Derek, We can use the two-entry (vector?) form: ?ArcTan "ArcTan[z] gives the arc tangent of the complex number z. ArcTan[x, y] gives \ the arc tangent of y/x, taking into account which quadrant the point (x, y) \ is in." Thus: ArcTan[0, 3] Pi/2 -- Allan --------------------- Allan Hayes Mathematica Training and Consulting Leicester UK www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565 "Blitzer" <drek1976 at yahoo.com> wrote in message news:8vfqv9$jif at smc.vnet.net... > 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 > > > >