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kaisan

verify: sin(x+y)-sin(x-y)=2cosxsiny

  • one year ago
  • one year ago

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  1. malexander
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    cos(x+y)=cosxacosy-sinxsiny cos(x-y)=cosxcosy+sinxsiny addition produces 2cosxcosy

    • one year ago
  2. lgbasallote
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    take the left hand side...do you know the formula for sin(x+y) and sin(x-y)?

    • one year ago
  3. malexander
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    Its an identity.

    • one year ago
  4. kaisan
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    i think so but i'm not sure

    • one year ago
  5. lgbasallote
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    sin(x+y) = sinxcosy + sinycosx sin(x-y) = sinxcosy - sinycosx can you do it from here?

    • one year ago
  6. kaisan
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    it looks familiar but i can't figure it out. is it one of the cosine identities?

    • one year ago
  7. lgbasallote
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    no...you substitute those into your problem sin(x+y) - sin (x-y) = sinxcosy + cosxsiny - (sinxcosy - cosxsiny)

    • one year ago
  8. kaisan
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    i'm still confused

    • one year ago
  9. lgbasallote
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    with what?

    • one year ago
  10. kaisan
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    how to do all of this in general

    • one year ago
  11. lgbasallote
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    basically you memorize the identities...

    • one year ago
  12. lgbasallote
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    i did not do anything fancy...all i did was substitute identities

    • one year ago
  13. kaisan
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    oh ok

    • one year ago
  14. lgbasallote
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    so regarding this problem...you're good?

    • one year ago
  15. kaisan
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    not really...

    • one year ago
  16. lgbasallote
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    sinxcosy + cosxsiny - (sinxcosy - cosxsiny) sinxcosy = cosxsiny - sinxcosy + cosxsiny

    • one year ago
  17. lgbasallote
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    that's a + not an =

    • one year ago
  18. kaisan
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    i don't understand what you did

    • one year ago
  19. lgbasallote
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    i distributed the minus sign

    • one year ago
  20. kaisan
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    oh ok i see

    • one year ago
  21. lgbasallote
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    so you're good now?

    • one year ago
  22. kaisan
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    yes thanks ^^

    • one year ago
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