       Re: Problem with finding angles between points in Cartesian plane

• To: mathgroup at smc.vnet.net
• Subject: [mg26119] Re: Problem with finding angles between points in Cartesian plane
• From: "Paul Lutus" <nospam at nosite.com>
• Date: Tue, 28 Nov 2000 01:56:05 -0500 (EST)
• References: <8vfqv9\$jif@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```"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.

In:=
For[a = 0,a <=360,
x = Cos[a Degree];
y = Sin[a Degree];
q = ArcTan[x,y] / Degree;
q = If[q < 0,360+q,q];
Print[a," ",N[q]];
a += 45]

-- prints the input and output angles in the range 0 - 360 degrees.

--

Paul Lutus
www.arachnoid.com

```

• Prev by Date: Re: Simplifying with positive constants
• Next by Date: Re: question RE: difference equations
• Previous by thread: Re: Problem with finding angles between points in Cartesian plane
• Next by thread: Re: Problem with finding angles between points in Cartesian plane