Quantcast

A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

kaylala

  • 2 years ago

Trigonometric Equation 2sin^2A + cosA + 1 = 0

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

    use the relation, \(\Large \sin^2A+\cos^2A=1\) to get a quadratic equation in only cos A

  2. kaylala
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    How's that @hartnn I really dont know

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

    2sin^2A + cosA + 1 = 0 2 (1- cos^2 A) +cos A +1 =0 did u get this?

  4. kaylala
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Yes. Got that part Then what? @hartnn

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

    right, now thats an quadratic equation in cos A. imagine you put cos A = x 2(1-x^2)+x+1 =0 can you bring that in the form of ax^2+bx+c=0 ?

  6. kaylala
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Okay. Will it be -2x^2+x+3 ? @hartnn

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

    yes, or you can write that as 2x^2-x-3=0 too can you solve this quadratic?

  8. kaylala
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I dont know for cosA=3/2 ??? But for cos A=-1 A={180} It it correct? @hartnn

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

    if you need solutions in the range 0 to 360, then yes, A = 180 is correct. else, the general form will be A = 180 \(\pm\) 360n

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

    as for cos A = 3/2 recollect that cos A can never be greater than 1 as the range of cos function is -1 to 1 so, cos A = 3/2 will have no solution :)

  11. kaylala
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    else, the general form will be A = 180 ± 360n What does that mean??? ^ So A is just 180 nothing else? @hartnn

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

    with cos A = -1 you got A = 180, right ? what about when A = 180+360 = 540 ? is cos 540 also = -1 ? if yes, why don't you consider it as a solution ? similarly for 180-360,180+2*360, 180-2*360 and so on (we don't consider them as the solution only when it is given that the range of A is from 0 to 360....and in that case only 180 is your answer :) )

  13. kaylala
    • 2 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Okay. I see. Thank you

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

    welcome ^_^

  15. 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.