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  1. Newsgroups: comp.graphics
  2. Path: sparky!uunet!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!att!fang!tarpit!bilver!syscon!nstar!miles!sjm
  3. From: sjm@miles.com (Scott Mark)
  4. Subject: Re: Angle between two coordinate locations
  5. Message-ID: <1992Jul24.124253.26240@miles.com>
  6. Organization: Miles Inc., Diagnostics Division, Elkhart, IN
  7. References: <l6faduINN8f0@girtab.usc.edu> <stare.18.0@edstar.rl.af.mil> <1992Jul22.234146.5571@uniwa.uwa.edu.au>
  8. Date: Fri, 24 Jul 1992 12:42:53 GMT
  9. Lines: 42
  10.  
  11. In article <1992Jul22.234146.5571@uniwa.uwa.edu.au> watson@maths.uwa.oz.au (David Watson) writes:
  12.  
  13. [Many interpretations of picture given]
  14.  
  15. I think by now someone should have guessed that the angle intended is between
  16. the line <X2,Y2>-><X1,Y1> and the line <X2,Y2>-><infinity,Y2>.
  17.  
  18.  
  19.  
  20. The original image, embellished with 3rd point:
  21.  
  22. >>>I have a problem where I need to obtain the angle between two points
  23. >>>on the screen.  For instance:
  24. >
  25. >>>        +------------------------------------------+
  26. >>>        |   * <-point 1                            |
  27. >>>        |                                          |
  28. >>>        |                                          |
  29. >>>        |                                          |
  30. >>>        |                                          |
  31. >>>        |                                          |
  32. >>>        |                                          |
  33. >>>        |                   * <-point 2            |   * <-point 3
  34. >>>        |                                          |
  35. >>>        +------------------------------------------+
  36. >
  37. >>>I would expect the function to return the angle as being 135 degrees
  38. >>>( or should if my picture was accurate )  Any help would be greatly
  39. >>>appreciated.  Thanks
  40. >
  41. >>I'm a little confused, How do you define an angle between two points without
  42. >>first defining the location of the vertex.  Is the vertex just assumed to be
  43. >>the origin (0,0)?
  44. >>Edward M.Starczewski       email: stare@lonex.rl.af.mil
  45. >
  46. >I wondered about that too, but if it were (0,0) the angle returned
  47. >would be less than 135 degrees.
  48. >Give us a clue, Randi
  49.  
  50.  
  51. Scott Mark
  52. sjm@miles.com
  53.