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Homework Help: Help With Complex Numbers

  1. Aug 13, 2010 #1
    1. The problem statement, all variables and given/known data

    I was trying to do this problem and noticed that I should be able to express SQRT(27) in terms of i and cancle out the i making it more simple I can't seem to remember how to do this thanks


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    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Aug 13, 2010 #2
    here you go sorry about that

    [PLAIN]http://img294.imageshack.us/img294/5396/captureow.jpg [Broken]

    i need to solve for x don't remeber how to do this
    Last edited by a moderator: May 4, 2017
  4. Aug 13, 2010 #3
    Last edited by a moderator: May 4, 2017
  5. Aug 13, 2010 #4


    Staff: Mentor

    If you're looking for the solutions to x2 - 27 = 0, they are the real numbers [itex]x = 3\sqrt{3}[/itex] and [itex]x = -3\sqrt{3}[/itex]. Otherwise, I have no idea what you're trying to do.
  6. Aug 13, 2010 #5
    I think i may have just proved
    SQRT(27) = -27
    did something wrong but I did it step by step let me look at this :(
  7. Aug 13, 2010 #6
    I'll show you in a moment I think i may have just proved SQRT(27) = -27
    I don't think I have done anything wrong this is really weird let me type it up... hope I'll find something wrong because if i don't... :O
  8. Aug 13, 2010 #7
    Last edited by a moderator: May 4, 2017
  9. Aug 13, 2010 #8
    Last edited by a moderator: May 4, 2017
  10. Aug 13, 2010 #9
    but ya that form is better to use becasue then you can cancel out the pi and your left with i raised to some fraction much easier to evalute no? but ya i guess i misse dup some where and did it wrong but it works
  11. Aug 13, 2010 #10
    well that sure is strange I never was taught that form of sin I just wen through the derrivation i guess of euelr's sine formula and screwed up somewhere but it's right

    wounder why I have never encountered it before i think it would be much easier to use no
  12. Aug 13, 2010 #11
    I think I have messed up when I did SQRT(3) as an example sorry
  13. Aug 13, 2010 #12
    Well see what I think I need to do is take my sine equation and set it equal to sqrt(37) sine can take on any value those who say it's llimited betweeen 1 and negative one are liers... and then solve so when solved earlier I think I was doing it right I thinkI just need to start over
  14. Aug 13, 2010 #13
    well i guess in theory I should have just done this

    http://img706.imageshack.us/img706/4708/capturefeb.jpg [Broken]

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    and solved for x since sine can take on any value it wants then just do sin(x) would truely be the most simplifed huh?
    I think that would be a better way to do it instead of setting it equal to sqrt(27) yes I know realize I forgot the initial 1/2 when I original atempted and set it eqaul to sqrt(27) so should i set it equal to sqrt(27) or just the whole darn thing
    Last edited by a moderator: May 4, 2017
  15. Aug 13, 2010 #14
    I take that back what I originally did wasn't wrong as that should be able to take on any number that it desires as well no and then I could cancel out the i if I had one in the denomenator, in post number seven I guess I just did something wrong...
  16. Aug 13, 2010 #15
    well i just had this great idea that I'm going to work out tommarow Im going to set cosine=sine
    yes that's
    or in common terms what angle does cosine and sine have the same value... none? Don't think so my freind I'm not buying it... I just woundering what will happen im going to solve it...

    sorry by the way i started out trying to do that problem then got into sine and this idea just poped into my head and was like well i should be able to solve that technically speaking...

    well i just did it everything canceled out I wounder what that means oh crap maybe you guys were right there is none =(
  17. Aug 14, 2010 #16


    Staff: Mentor

    This is ridiculous. If this were true, the 27 = (-27)2 would also be true. Obviously, it isn't.

    sqrt(27) is not a complex number, so why are you even bothering to go down that path?

    In its simplest form, sqrt(27) is 3sqrt(3).
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