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: Trigonometric problem

  1. May 25, 2004 #1
    How to solve: sin x + sin 3x + sin 2x = 1 + cos 2x + cos x, give general solution in radians for x.
    How to get start?
    Anyone could help me, please?
  2. jcsd
  3. May 25, 2004 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    You will need the following identities:
  4. May 26, 2004 #3
    I have solved the problem. I have used the identities:
    sin x + sin y = 2 sin (x+y)/2 cos(x-y)/2 and cos 2x = 2 cos^2 (x) - 1.
    With these two identities, it's easy to solve the problem.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook