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  1. #1
    1/2 man,1/2 bear,1/2 pig ManBearPig's Avatar
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    Math Majors -- simplify this

    If you can, please simplify this expression:

    SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))



    The expression in the COS( ) looks familiar to me, but it has been 10 years since I finished my engineering degree. Thanks!
    ...

  2. #2
    Hazardous Taerom's Avatar
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  3. #3
    You Know!? For Kids! jsharr's Avatar
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    Quote Originally Posted by Towlie
    If you can, please simplify this expression:

    SATAN



    The expression in the COS( ) looks familiar to me, but it has been 10 years since I finished my engineering degree. Thanks!
    I removed all the unnecesasry stuff and got the answer to your math problem
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    Quote Originally Posted by colorider View Post
    Phobias are for irrational fears. Fear of junk ripping badgers is perfectly rational. Those things are nasty.

  4. #4
    1/2 man,1/2 bear,1/2 pig ManBearPig's Avatar
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    Please, express the answer in terms of X and Y only; no supernatural deities.
    ...

  5. #5
    phony collective progress x136's Avatar
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    Who is this Y? Is she hot?

  6. #6
    On my TARDIScycle! KingTermite's Avatar
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    Quote Originally Posted by Taerom
    42
    +1


    Do your own math homework.
    Quote Originally Posted by coffeecake View Post
    - it's pretty well established that Hitler was an *******.

  7. #7
    1/2 man,1/2 bear,1/2 pig ManBearPig's Avatar
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    This ain't homework. The question is directed to math majors, not math phobics. This is not an advanced problem in the grand scheme of things; I am simply rusty on my trig and algebra.
    ...

  8. #8
    Senior Member scrapmetal's Avatar
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    Quote Originally Posted by Taerom
    42
    what else ..... and thanks for the fish.

  9. #9
    On my TARDIScycle! KingTermite's Avatar
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    Quote Originally Posted by Towlie
    This ain't homework. The question is directed to math majors, not math phobics. This is not an advanced problem in the grand scheme of things; I am simply rusty on my trig and algebra.
    No it's not advanced....never said it was. I'm not a math phobic by ANY stretch of the definition (I have a bachelors and masters degree in computer engineering...methinks I've taken some math courses).....I still think it looks like you are trying to get help with a homework problem.
    Quote Originally Posted by coffeecake View Post
    - it's pretty well established that Hitler was an *******.

  10. #10
    1/2 man,1/2 bear,1/2 pig ManBearPig's Avatar
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    I am 33 yrs old; I am not doing homework; I am a BSME (UT Austin, May, 1997)....I derived this expression trigonometrically on a project I am working on, and I don't know/remember how to simplify it.

    I don't remember all the trigonometric identities because I haven't worked with them for a long while, e.g.

    http://www.sosmath.com/trig/Trig5/trig5/trig5.html
    ...

  11. #11
    Videre non videri
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    Quote Originally Posted by KingTermite
    Quote Originally Posted by Taerom
    42
    +1
    43!

    I don't think I could simplify it further myself, but I'm not very good at math anyway. Why can't you use it as it is?

  12. #12
    1/2 man,1/2 bear,1/2 pig ManBearPig's Avatar
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    I guess I could - but if there were a generally known trigonometric identity in the field, it might look dumb for me to express it in an unnecessarily complicated fashion (e.g., to make something up, suppose everythinig in the parantheses could be replaced by cos(x/y) or something simple like that).
    ...

  13. #13
    On my TARDIScycle! KingTermite's Avatar
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    Quote Originally Posted by Towlie
    I am 33 yrs old; I am not doing homework; I am a BSME (UT Austin, May, 1997)....I derived this expression trigonometrically on a project I am working on, and I don't know/remember how to simplify it.

    I don't remember all the trigonometric identities because I haven't worked with them for a long while, e.g.

    http://www.sosmath.com/trig/Trig5/trig5/trig5.html
    I'm only calling it how it looked. See it from "our" point of view. Too many kids come on here and try to get help with their homework....quite often. It would be good for you to explain your situation so we don't think (like I did) that you are a 16 year old looking for homework help. I'm sorry if I offended....but that sure is how it looked.
    Quote Originally Posted by coffeecake View Post
    - it's pretty well established that Hitler was an *******.

  14. #14
    Senior Member mtnbk3000's Avatar
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    Quote Originally Posted by scrapmetal
    what else ..... and thanks for the fish.
    whats up with people and hitchikers guide to the galaxy
    hi

  15. #15
    Senior Citizen lyeinyoureye's Avatar
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    If you actually have a BSME, then you should now how to do this as a matter of course imo. Nothing scares me more than engineering majors that don't know their shiz, because it's an applied skill. Unlike something like english, or even pure math, where screw ups can result in poor marks or scathing peer reviews, but shiz can't really go that bad from a practical perspective. Heh, ManBearPig.

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    '05 NUEser EJ123's Avatar
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    Answers.yahoo.com

  17. #17
    The Site Administrator: Currently at home recovering from a couple of strokes,please contact my assistnt admins for forum issues Tom Stormcrowe's Avatar
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    Quote Originally Posted by Towlie
    If you can, please simplify this expression:

    SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))



    The expression in the COS( ) looks familiar to me, but it has been 10 years since I finished my engineering degree. Thanks!
    (XY)1/2*COS[45-ATANG(Y/X)]
    =(XY)(XY)(COS)(45-X/Y)?

    I think that's how it would factor out.
    on light duty due to illness; please contact my assistants for forum issues. They are Siu Blue Wind, or CbadRider or the other 3 star folk. I am currently at home recovering from a couple of strokes. I am making good progress, happily.


    . He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.- Fredrick Nietzsche

    "We can judge the heart of a man by his treatment of animals." - Immanuel Kant

  18. #18
    Senior Member
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    It'll give you the length of the vector from the origin to (x,y) projected onto the line x = y.

    Though that might be how you derived it in the first place! Simplifying it?
    Hmm, thinking dot product could be useful, (also thinking as typing so bear with me).

    (x,y).(0.707, 0.707) = 0.707x + 0.707y

    excel confirms.
    where 0.707 is actually meant to be 1/sqrt(2)


    Possible complications outside of the range 0-90 degrees due to the atan not being unique. Can't be bothered to think that hard though.


    Apologies to those arguing the poster should have solved it themselves. But I needed some mental exercise due to having been laid up in hospital for four weeks avoiding my maths lectures.




    edit:

    Just managed it properly too.
    let sqrt() denote SQRT(X^2 + Y^2) for easy writing.

    SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))

    =sqrt() * [ cos(45)*cos(atan(y/x) + sin(45)*sin(atan(y/x)]
    =sqrt() * [ 0.707 * x / sqrt() + 0.707 * y / sqrt() ]
    =0.707 * (x + y)
    Last edited by j-dowsett; 05-22-07 at 08:01 AM.

  19. #19
    1/2 man,1/2 bear,1/2 pig ManBearPig's Avatar
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    Quote Originally Posted by j-dowsett
    It'll give you the length of the vector from the origin to (x,y) projected onto the line x = y.

    Though that might be how you derived it in the first place! Simplifying it?
    Hmm, thinking dot product could be useful, (also thinking as typing so bear with me).

    (x,y).(0.707, 0.707) = 0.707x + 0.707y

    excel confirms.
    where 0.707 is actually meant to be 1/sqrt(2)


    Possible complications outside of the range 0-90 degrees due to the atan not being unique. Can't be bothered to think that hard though.


    Apologies to those arguing the poster should have solved it themselves. But I needed some mental exercise due to having been laid up in hospital for four weeks avoiding my maths lectures.




    edit:

    Just managed it properly too.
    let sqrt() denote SQRT(X^2 + Y^2) for easy writing.

    SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))

    =sqrt() * [ cos(45)*cos(atan(y/x) + sin(45)*sin(atan(y/x)]
    =sqrt() * [ 0.707 * x / sqrt() + 0.707 * y / sqrt() ]
    =0.707 * (x + y)

    Thanks, man. I actually logged in because I found the answer on my own and wanted to post it. The result I found was (X+Y) / SQRT(2). Soooooo simple. I found the answer numerically, plugging in numbers into a table and playing around with them.
    ...

  20. #20
    Feral Member Nicodemus's Avatar
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    ouch. math. I mean, I love it and all but I've done my time. University flashbacks
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  21. #21
    Senior Member joeprim's Avatar
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    Quote Originally Posted by Towlie
    If you can, please simplify this expression:

    SQRT(X^2 + Y^2) * COS(45 - ATAN(Y/X))



    The expression in the COS( ) looks familiar to me, but it has been 10 years since I finished my engineering degree. Thanks!
    Where are you trying to get to? The Atan will give you and angle that you then subtract from 45 get the Cos of that ...
    So as long as you know x&y things should be ok. Or are you trying to use this to determine x&y?

    Joe

  22. #22
    Fourth Degree Legend junkyard's Avatar
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    42
    4*2
    8
    Quote Originally Posted by dminor View Post
    The caveat with a strap-on, of course, is you will have to get creative with a couple of lock cables and an anchor point

  23. #23
    The Site Administrator: Currently at home recovering from a couple of strokes,please contact my assistnt admins for forum issues Tom Stormcrowe's Avatar
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    Quote Originally Posted by joeprim
    Where are you trying to get to? The Atan will give you and angle that you then subtract from 45 get the Cos of that ...
    So as long as you know x&y things should be ok. Or are you trying to use this to determine x&y?

    Joe
    I have no idea, I got lost at that point!
    on light duty due to illness; please contact my assistants for forum issues. They are Siu Blue Wind, or CbadRider or the other 3 star folk. I am currently at home recovering from a couple of strokes. I am making good progress, happily.


    . He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.- Fredrick Nietzsche

    "We can judge the heart of a man by his treatment of animals." - Immanuel Kant

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