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hannahg Group Title

Find all solutions in the interval [0, 2π). sin2x + sin x = 0

  • one year ago
  • one year ago

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  1. .Sam. Group Title
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    Do you know what's the identity for sin2x?

    • one year ago
  2. hannahg Group Title
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    noo i forgot..

    • one year ago
  3. .Sam. Group Title
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    sin2x=2sinxcosx

    • one year ago
  4. .Sam. Group Title
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    So how do you proceed?

    • one year ago
  5. hannahg Group Title
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    2sinx+cosx+sinx=0 right? what do i do next?

    • one year ago
  6. .Sam. Group Title
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    no, it should be from sin2x + sin x = 0 to 2sinxcosx + sin x =0 right?

    • one year ago
  7. hannahg Group Title
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    ohh yea

    • one year ago
  8. .Sam. Group Title
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    you should try factoring now

    • one year ago
  9. hannahg Group Title
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    sinx(2cosx+1)=0 is this right? what do i do next? o.O

    • one year ago
  10. AravindG Group Title
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    ya u r right :)

    • one year ago
  11. .Sam. Group Title
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    yes, now you can let sinx=0 and 2cosx+1=0 then find the x values

    • one year ago
  12. AravindG Group Title
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    equate that to 0 and find x values

    • one year ago
  13. hannahg Group Title
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    so i got cosx=-1/2 how do i find the value of x?

    • one year ago
  14. .Sam. Group Title
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    well you can do this cosx=-1/2 x=cos^{-1} (-1/2)

    • one year ago
  15. hannahg Group Title
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    so what are all possible values of x? 0 and......what else O.o

    • one year ago
  16. AravindG Group Title
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    @hannahg :) instead of o.O

    • one year ago
  17. .Sam. Group Title
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    no its not 0

    • one year ago
  18. hannahg Group Title
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    @AravindG :)

    • one year ago
  19. .Sam. Group Title
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    you calculate cos^(-1) 1/2 first without minus on half you'll get 60 degrees

    • one year ago
  20. hannahg Group Title
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    yes:)

    • one year ago
  21. .Sam. Group Title
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    then use this chart for cosine |dw:1358873950517:dw| we are looking at the minus side since we got minus half. then 180-60=120 degrees 180+60=240 degrees

    • one year ago
  22. AravindG Group Title
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    @hannahg thats better :)

    • one year ago
  23. hannahg Group Title
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    yes. so all the possible solutions will be pi, pi/3, 2pi/3?

    • one year ago
  24. .Sam. Group Title
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    you still have sinx=0 to do

    • one year ago
  25. hannahg Group Title
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    yes......! so 0?

    • one year ago
  26. .Sam. Group Title
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    yes but dont forget about 180

    • one year ago
  27. .Sam. Group Title
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    |dw:1358874634831:dw|

    • one year ago
  28. .Sam. Group Title
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    since theta is 0, then you get 180

    • one year ago
  29. hannahg Group Title
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    @.Sam. so what are all solutions in the interval??

    • one year ago
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