Quantcast

A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

shaqadry

  • 2 years ago

how to solve 3 sin^2 2x + 2 cos 2x - 2 = 0

  • This Question is Closed
  1. Azteck
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[3\sin^{2}(2x)= 3(1-\cos^{2}(2x))\] \[=3-3\cos^2(2x)\] ---------------------------------------------------------------------- \[3-3\cos^2(2x)+2cos(2x)-2=0\] Collect like terms and move everything to the RHS \[3\cos^2(2x)-2cos(2x)-1=0\] Let u=cos(2x) \[3u^2-2u-1=0\] Solve the quadratic.

  2. shaqadry
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i dont get it, what happen to sin^2 2x?

  3. shaqadry
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    oh wait just got it!

  4. Azteck
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Yeah I just made sin^2(2x) in terms of cos(2x).

  5. Azteck
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    So could you solve that quadratic and then after you have the values of u, bring back the cos(2x) by replacing u with cos(2x).

  6. Azteck
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Then after you've done that, solve normally as if it were cos(x) and then after you get the angles, divide by 2 because you're finding x, not 2x.

  7. Azteck
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    If you're unclear about what you're supposed to do, let me know.

  8. shaqadry
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    okay thanks! i really didnt know how to solve that part bcs it has 2x

  9. shaqadry
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    wait i'll try and calculate the angle

  10. shaqadry
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    the angles i got are 0, 54.75, 125.25, 180, 234.75, 305. 25 and 360

  11. Azteck
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Awesome work. That's pretty much all of them. I think you need to work on your rounding up. Because for some of the angles, I got either 0.01 more or less than your angles.

  12. Azteck
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Ah I see, you rounded up before dividing by 2. That's okay. You're still correct. I just prefer to round up at the end result.

  13. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.