Math help[NA]

Discussion in 'Technical Corner' started by Let'sgoflying!, Nov 29, 2021.

  1. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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    Known plots:
    X=966 Y=8.54
    X=1299 Y=7.87
    I need an equation where I enter X each time to figure Y
    Tks
    Too many decades since I did this
    Real world need, not hypothetical
     
  2. jimhorner

    jimhorner Line Up and Wait

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    Assuming a linear fit, 2 points only:

    slope m = (y1 - y2)/(x1 - x2)

    m = (8.54 - 7.87)/(966 - 1299) = -2.01e-3

    y = mx + b => b = y - mx

    choose any point:

    b = 8.54 - (-2.01e-3 * 966) = 10.5

    so y = -2.01e-3 x + 10.5

    I've kept each of the calculated values to 3 sigdigs.
     
    Last edited: Nov 29, 2021
  3. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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    Yes linear

    y = -2.01e-3 + 10.5

    might need help with the
    “ -2.01e-3 “
     

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  4. kath

    kath Administrator Management Council Member PoA Technical Administrator

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    -2.01e-3 is -0.00201
     
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  5. eman1200

    eman1200 Touchdown! Greaser! PoA Supporter

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    Bro do you even lift
    the volume of a thick crust pizza with height "a" and radius "z" is π·(radius)2·(height), or pi*z*z*a.

    also, I had pizza for dinner.
     
  6. jimhorner

    jimhorner Line Up and Wait

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    -0.00201

    And I should have written:

    y = -2.01e-3x + 10.5

    I forgot the x when I orignally posted. It's corrected now


    Sent from my iPhone using Tapatalk Pro
     
  7. nauga

    nauga Administrator Management Council Member PoA Technical Administrator

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    Rotate your phone 90 deg. ;)

    Nauga,
    and his direction cosine matrix
     

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  8. Half Fast

    Half Fast Final Approach

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    Try using quaternions instead. Less processing, and you’ll avoid gimbal lock.

    Half-Fast,
    Retired servo geek
     
  9. jimhorner

    jimhorner Line Up and Wait

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    Or download pcalc. RPN!

    [​IMG]
     
  10. asicer

    asicer Final Approach

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    Looks like a seagull flying over a lopsided pine tree...
    upload_2021-11-29_18-12-39.png
     
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  11. Rushie

    Rushie En-Route

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    I had my cell years before I figured that out.
     
  12. ColoPilot

    ColoPilot Line Up and Wait

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    I learned in college -- if you expect the results to be a straight line, only plot 2 points.
     
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  13. Half Fast

    Half Fast Final Approach

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    I learned it as, “Two points define a line and three points don’t. Three points define a plane and four points don’t.”
     
  14. Let'sgoflying!

    Let'sgoflying! Touchdown! Greaser! PoA Supporter

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  15. Piperonca

    Piperonca Line Up and Wait PoA Supporter

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  16. Piperonca

    Piperonca Line Up and Wait PoA Supporter

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    Last edited: Nov 30, 2021
  17. Capt. Geoffrey Thorpe

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  18. Piperonca

    Piperonca Line Up and Wait PoA Supporter

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    Go Pylab for free
     
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  19. nauga

    nauga Administrator Management Council Member PoA Technical Administrator

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    [966 1;1299 1]\[8.84;7.87] :cool:

    ETA a colon for a column vector.

    Nauga,
    from the geek farm
     
    Last edited: Nov 30, 2021
  20. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    Error using \
    Matrix dimensions must agree.



     
    Last edited: Nov 30, 2021
  21. Salty

    Salty Touchdown! Greaser!

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    One point defines a line if the line is going directly away from you.
     
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  22. Piperonca

    Piperonca Line Up and Wait PoA Supporter

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    You make a good point.
     
  23. Bob Noel

    Bob Noel Touchdown! Greaser!

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    or if the line has zero length
     
  24. GaryM

    GaryM Pattern Altitude

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    I see what you did there.
     
  25. Piperonca

    Piperonca Line Up and Wait PoA Supporter

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    Let's get this straight...don't want any pointless discussion, y'all hear?
     
  26. Half Fast

    Half Fast Final Approach

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    I think he’s just feeding us a line.
     
  27. Half Fast

    Half Fast Final Approach

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    That would be a segment. A line has infinite length.
     
  28. Piperonca

    Piperonca Line Up and Wait PoA Supporter

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    Kind of like this thread...
     
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  29. ColoPilot

    ColoPilot Line Up and Wait

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    Infinite length and no point
     
  30. Piperonca

    Piperonca Line Up and Wait PoA Supporter

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    Folks, I think we’re done here. End of the line.
     
  31. Half Fast

    Half Fast Final Approach

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    Thanks for the ray of hope.
     
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  32. Pugs

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    Kids and their "software this and software that". :rolleyes:


    [​IMG]
     
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  33. Half Fast

    Half Fast Final Approach

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    Bought my HP-15C shortly after college graduation. It carried me through 36 years of engineering practice at Lockheed and it’s still going strong now that I’m doing pro bono stuff.

    They don’t build ‘em like that anymore and that’s a real shame.
     
  34. Pugs

    Pugs Cleared for Takeoff PoA Supporter

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  35. nauga

    nauga Administrator Management Council Member PoA Technical Administrator

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    D'oh. Added a missing semicolon.

    Nauga,
    punctually
     
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  36. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser! PoA Supporter

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    ans =

    -0.0029
    11.6539

    :)
     
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  37. nauga

    nauga Administrator Management Council Member PoA Technical Administrator

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    Oh FFS...(corrections in red)
    [966 1;1299 1]\[8.54;7.87]
    Code:
    [966 1;1299 1]\[8.54;7.87]
    
    ans =
    
       -0.0020
       10.4836
    
    >>
    Nauga,
    who is better with Matlab than typing o_O
     
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  38. Rich Holt

    Rich Holt Line Up and Wait

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    Hey, I was a Kat!! Also, I have that patch in a frame on my wall.
     
  39. Rich Holt

    Rich Holt Line Up and Wait

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    Photomath is the real answer to sleeping through math class. Point. Shoot. Solved.
    upload_2021-11-30_16-9-25.png
     
  40. flyingbrit

    flyingbrit Pre-takeoff checklist

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    OP, e-3 means "times 10 to the -3 power", i.e. move the decimal point three places left. It became common with computers, which don't handle superscripts. IIRC, I first encountered this when using Lotus 1-2-3 in the 1980s. Here is a Wiki page which addresses this; look about 1/3 the way down:

    https://en.wikipedia.org/wiki/Scientific_notation
     
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