       Re: Plot Angle between Vectors

• To: mathgroup at smc.vnet.net
• Subject: [mg62091] Re: Plot Angle between Vectors
• From: Peter Pein <petsie at dordos.net>
• Date: Fri, 11 Nov 2005 02:51:54 -0500 (EST)
• References: <dkuvk6\$7pj\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Florian schrieb:
> I am a newbie to Mathematica, and i try to plot two vectors with the
> angle in-between. I could not find a code how to plot angles at all!
> Would be great if someone could help! Thanks a lot.
>

Hi Florian,

the following function constructs a Graphics object containing 2 Arrows
and an arc from the first to the second vector:

In:=
VectorAngle[v1_,v2_]:=
Graphics[Append[Arrow[{0,0},#]&/@{v1,v2},
Circle[{0,0},Sqrt@Min[#1^2+#2^2&@@@{v1,v2}]/5,
If[GreaterEqual@@##,{0,2Pi}+##,##]&[ArcTan@@@{v1,v2}]]]]

an example:

In:=
FullForm[VectorAngle[{3, 2}, {-1, 4}]]
Out//FullForm=
FullForm[Graphics[
{Arrow[{0, 0}, {3, 2}], Arrow[{0, 0}, {-1, 4}],
Circle[{0, 0}, Sqrt/5, {ArcTan[2/3], Pi - ArcTan}]}]]

usage:

Show[VectorAngle[{3, 2}, {-1, 4}], AspectRatio -> 1, Axes -> True]

or

Show[VectorAngle[{-1, 4}, {3, 2}], AspectRatio -> 1, Axes -> True]

Peter

```

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