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!

3 Equations + sine : Help

  1. May 25, 2004 #1
    Could someone help me find the solution of this ?

    x - y + z - 2 A sin(y+z) = C
    -x - y - z - 2 A sin(x+z) = C
    -x + y + z - 2 A sin(x+y) = C

    Where C and A are constant ?
    Many thanks
  2. jcsd
  3. May 25, 2004 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    could you please confirm that the second line is not x + y - z ...
  4. May 26, 2004 #3
    Sorry, based on your question, I did my calculations again and ... The real system is:

    -x + y + z + 2A sin(y-z) = C
    -x + y - z + 2A sin(x-z) = C
    x + y - z + 2A sin(x-y) = C

    where A and C are constant.

    Could you please help me?
  5. May 26, 2004 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I would start by applying the trigonometric identities for sin(a+b) then add the first 2 equations together. I think several terms will drop out, you then should be able to repeat the process with the 3rd equation. The goal is to eliminate one of the variables, when you have an expression involving 2 variables solve for 1 of them, then use that to back substitute isolating the remaining variables.
  6. May 27, 2004 #5
    5 unkowns
    2 of which are constant
    3 equations

    combine 3 equations, you will be left with 2 unkowns (your two constants)

    And you are done.... all you need is the time to solve it.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook