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: Solve give me some help

  1. Feb 27, 2005 #1
    Solve plz give me some help

    how would you solve this question cos2x+cosx+1=0? The cos2x is throwing me off is that the same as cos^2x? Its multiple choice and all the answers are in radian how come?
    Last edited: Feb 27, 2005
  2. jcsd
  3. Feb 27, 2005 #2


    User Avatar
    Science Advisor
    Homework Helper

    1. cos(a + b) = cos(a)cos(b) - sin(a)sin(b).
    2. Do you know how to write 1 in terms of sin and cos?
  4. Feb 27, 2005 #3
    no i dont plz help me
  5. Feb 27, 2005 #4
    [tex]\sin^{2}x + \cos^{2}x = 1[/tex]
  6. Feb 27, 2005 #5
    cos2x is not the same as cos^2x. Use a double angle identity for that one.
  7. Feb 28, 2005 #6


    User Avatar
    Science Advisor
    Homework Helper

    On normal basis,u should end up with a simple quadratic equation is "\cos x"...That won't be 2 hard to solve...

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