Deriving an angle from three points

[James Hurley]

>
> Message: 24
> Date: Tue, 15 Dec 2009 22:21:47 -0800
> From: Mark Swindell <mdswindell at cruzio.com>
> Subject: Deriving an angle from three points
> To: How to use Revolution <use-revolution at lists.runrev.com>
> Message-ID: <B3725793-6274-4F53-91D2-3154D31F9CDF at cruzio.com>
> Content-Type: text/plain;	charset=us-ascii
>
> 40,116
> 98,186
> 132,118
>
> How would one determine the angle created from three points, such as  
> those above?
>
> Thanks,
> Mark
>

Mark,

Here is how easy this is in Turtle Graphics:

on mouseUp
    startTurtle --Initiates the turtle graphics library
    penup
    setxy 40,116
    pendown
   put direction(98,186) into tStartAngle
   setxy 98,186
   put direction(132,118) into tEndAngle
   setxy 132,118  --Not necessary, but visually satisfying
   put tEndAngle - tStartAngle into dA
   put dA & cr & 360 - da  into msg box
   choose the browse tool
end mouseUP

(Assuming your middle point is the apex of the angle you want.)

To run this you will need the TG library. Run this in the msg box

go url "http://www.jamesphurley.com/jhurleyFolder/TurtleGraphics.rev"

Jim Hurley