1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    Uploaded with ImageShack.us

    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]

    Uploaded with ImageShack.us

    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).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook