A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous97

  • one year ago

If sin Θ = 2 over 7 and tan Θ > 0, what is the value of cos Θ?

  • This Question is Closed
  1. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so do you know SOHCAHTOA?

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

    so if opposite over hypotenuse is 2/7 then cos is...

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

    it is still 2/7

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

    because sin and cos of one angle is the same

  5. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    one way to do it would be to use the identity cos^2 x = 1 - sin^2 x

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

    |dw:1439852492795:dw|

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

    |dw:1439852539120:dw|

  8. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    No Sammy not always true

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

    CAST rule for signs!!!

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

    why not?

  11. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    its only true for 45 degrees

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

    i dont think so

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

    oh i see

  14. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    |dw:1439852609072:dw|

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

    it will work why not just consider you working on first quadrant since tan>0 and sin>0 so must be first quad

  16. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    another way would be to use pythagoras theorem to find the adjacent side then cos = adj / hyp

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

    |dw:1439852745494:dw|

  18. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    true

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

    use Pythagoras to find x and then find cos theta

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

    but the easiest way is the use of identity cos^2+sin^2=1 like @welshfella said

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

    we can use that identity to find exact value of cos ?? aww never seen that before o.O

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

    yeah why not?

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

    you have sintheta =2/7 just put it into the equation and solve for cos

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

    ohh got it i forgot to take square root

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

    ah i see haha

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

    square root produces two values you have to consider tan>0 again

  27. anonymous97
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    A. 3 square root of 5 over 7 B. negative 3 square root of 5 over 7 C. 3 square root of 5 D. negative 3 square root of 5

  28. anonymous97
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    those are my answer choices

  29. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    cos^2 x = 1 - sin^2 x = 1 - 4/49 = 49/49 - 4/49 = 45/49 cos x = sqrt (45/49) can you finish this off?

  30. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    hint factor 45 and look for perfect squares

  31. 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.