Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

shaqadry

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

  • one year ago
  • one year ago

  • This Question is Closed
  1. Azteck
    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.

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

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

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

    oh wait just got it!

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

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

    • one year ago
  5. Azteck
    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).

    • one year ago
  6. Azteck
    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.

    • one year ago
  7. Azteck
    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.

    • one year ago
  8. shaqadry
    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

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

    wait i'll try and calculate the angle

    • one year ago
  10. shaqadry
    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

    • one year ago
  11. Azteck
    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.

    • one year ago
  12. Azteck
    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.

    • one year ago
    • Attachments:

See more questions >>>

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.