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anonymous

  • one year ago

Find an exact value. cos 15°

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  1. arindameducationusc
    • one year ago
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    cos(45-30) using cos(A-B)=cosAcosB+sinAsinB

  2. arindameducationusc
    • one year ago
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    Got?

  3. anonymous
    • one year ago
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    cos (45 - 30) = cos45cos30 + sin45sin30 ?

  4. arindameducationusc
    • one year ago
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    yes

  5. arindameducationusc
    • one year ago
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    Can you solve now?

  6. anonymous
    • one year ago
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    so then would it be cos (45-30) = (radical) 2 / 2 * (radical) 3 / 2 + (radical) 2 / 2 * 1 / 2 ?

  7. anonymous
    • one year ago
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    would it be \[\sqrt{6} + \sqrt{2} / 4\]

  8. arindameducationusc
    • one year ago
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    It should be Sqrt[3] - 1/2 Sqrt[2]

  9. arindameducationusc
    • one year ago
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    1/sqrt(2)*sqrt(3)/2 - 1/sqrt(2)*1/2

  10. arindameducationusc
    • one year ago
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    =sqrt(3)-1 / 2sqrt(2)

  11. arindameducationusc
    • one year ago
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    Got it?

  12. anonymous
    • one year ago
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    thats not one of my answer choices :(

  13. anonymous
    • one year ago
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    these are my answer choices

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  14. arindameducationusc
    • one year ago
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    okay let me see....

  15. anonymous
    • one year ago
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    @lxoser cos(15) To find this value, all you have to do is express 15 as a sum or difference of two known unit circle values. Then, take advantage of the sum/difference identities. cos(a + b) = cos(a)cos(b) - sin(a)sin(b) cos(a - b) = cos(a)cos(b) + sin(a)sin(b) [note: watch how the addition one uses subtraction, and subtraction uses addition] For this case, 15 = 45 - 30. Therefore, cos(15) = cos(45 - 30) And we know what the sine and cosine of 45 degrees and 30 degrees are. Using the cosine difference identity, we get cos(45)cos(30) + sin(45)sin(30) Which we know how to solve. (sqrt(2)/2) (sqrt(3)/2) + (sqrt(2)/2) (1/2) Keep simplifying, [ sqrt(6)/4 ] + [ sqrt(2) / 4 ] [sqrt(6) + sqrt(2)] / 4

  16. anonymous
    • one year ago
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    its A

  17. anonymous
    • one year ago
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    so i got it right the first time, thank you so much guys for your time & help! i understand now :-)

  18. anonymous
    • one year ago
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    i live in florida

  19. anonymous
    • one year ago
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    is that FLVS?

  20. anonymous
    • one year ago
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    lol, yes it is

  21. anonymous
    • one year ago
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    i completely agree!! lol

  22. anonymous
    • one year ago
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    i like how if you miss one you get an 80 on the homework

  23. anonymous
    • one year ago
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    yeah i know! like really?

  24. anonymous
    • one year ago
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    and it brings your grade down like 2-3 points but if you get a 100 it brings it up like .25

  25. anonymous
    • one year ago
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    lmao omg i feel your pain so much

  26. anonymous
    • one year ago
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    what math are you in

  27. anonymous
    • one year ago
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    what math are you in

  28. anonymous
    • one year ago
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    im in pre-cal honors

  29. anonymous
    • one year ago
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    if you go to google and type in flvs it got a 2.5 on google but flvs only shows the good ones on the side XD

  30. anonymous
    • one year ago
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    lol, really?? florida students got it rough lol

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