# Math help[NA]

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

1. ### 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. ### jimhornerLine 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!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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-2.01e-3 is -0.00201

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5. ### eman1200Touchdown! Greaser!PoA Supporter

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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. ### jimhornerLine 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

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Nauga,
and his direction cosine matrix

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8. ### Half FastFinal Approach

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

Half-Fast,
Retired servo geek

9. ### jimhornerLine Up and Wait

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10. ### asicerFinal Approach

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Looks like a seagull flying over a lopsided pine tree...

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11. ### RushieEn-Route

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I had my cell years before I figured that out.

12. ### ColoPilotLine 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 FastFinal 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!Touchdown! Greaser!PoA Supporter

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Thanks!!

15. ### PiperoncaLine Up and WaitPoA Supporter

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16. ### PiperoncaLine Up and WaitPoA Supporter

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Last edited: Nov 30, 2021
17. ### Capt. Geoffrey ThorpeTouchdown! Greaser!PoA Supporter

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Go Matlab or go home.

18. ### PiperoncaLine Up and WaitPoA Supporter

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

ETA a colon for a column vector.

Nauga,
from the geek farm

Last edited: Nov 30, 2021
20. ### Capt. Geoffrey ThorpeTouchdown! Greaser!PoA Supporter

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Error using \
Matrix dimensions must agree.

Last edited: Nov 30, 2021
21. ### SaltyTouchdown! Greaser!

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

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22. ### PiperoncaLine Up and WaitPoA Supporter

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You make a good point.

23. ### Bob NoelTouchdown! Greaser!

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or if the line has zero length

24. ### GaryMPattern Altitude

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I see what you did there.

25. ### PiperoncaLine Up and WaitPoA Supporter

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

26. ### Half FastFinal Approach

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I think he’s just feeding us a line.

27. ### Half FastFinal Approach

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

28. ### PiperoncaLine Up and WaitPoA Supporter

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29. ### ColoPilotLine Up and Wait

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Infinite length and no point

30. ### PiperoncaLine Up and WaitPoA Supporter

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

31. ### Half FastFinal Approach

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Thanks for the ray of hope.

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32. ### PugsCleared for TakeoffPoA Supporter

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Kids and their "software this and software that".

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33. ### Half FastFinal 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. ### PugsCleared for TakeoffPoA Supporter

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Bought this one in 1984 after my original 43C died. Still use it almost every day.

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Nauga,
punctually

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36. ### Capt. Geoffrey ThorpeTouchdown! Greaser!PoA Supporter

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ans =

-0.0029
11.6539

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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

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38. ### Rich HoltLine 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 HoltLine Up and Wait

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Photomath is the real answer to sleeping through math class. Point. Shoot. Solved.

40. ### flyingbritPre-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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