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: Trig. again

  1. Dec 11, 2009 #1
    1. The problem statement, all variables and given/known data
    this time i have posted two questions on a post, instead of me creating posts all over the forum.

    a)cot^2x + cosec^2x = 7
    b) (2 cosec^2)2x + cot2x =3
    find out the solutions.
    2. Relevant equations
    cosec^2 = 1+ cot^2


    3. The attempt at a solution
    a) cot^2x + cosec^2x = 7
    cosec^2-1 + cosec^2 = 7
    2cosec^2x = 8
    now i thought of solving it by the difference of squares?
    couldn't solve it =/
    b) totally cluesless as this one has 2 after function cot i.e cot2x =/
     
  2. jcsd
  3. Dec 11, 2009 #2

    Mark44

    Staff: Mentor

    It's not very clear what the equation above is saying. You are at least using parentheses, but not in the most helpful way.
    Is this supposed to be 2csc^2(2x) + cot(2x) = 3?

    If so, you should replace csc(2x) with 1/sin(2x) and cot(2x) with cos(2x)/sin(2x).
    So csc^2(2x) = 4
    Or 1/[sin^2(2x)] = 4
    Can you take it from there?
     
  4. Dec 11, 2009 #3
    sorry as i am pretty newbie with latex =/ hmm i dont get it, how did you end up with = 4? and yea i gotta say.. that question doesn't make sense well the way i typed makes it more complicated (looking)
     
  5. Dec 11, 2009 #4

    Mark44

    Staff: Mentor

    Divide both sides of the equation by 2 to get csc^2(2x) = 4.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook