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pottersheep Group Title

Stuck on Trig identities! :( Help please~ How do I prove cos(x+y)cosy + sin(x+y)siny = cosx??

  • 2 years ago
  • 2 years ago

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  1. tanjung Group Title
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    just to understanding the formula : cosAcosB + sinAsinB = cos(A-B)

    • 2 years ago
  2. pottersheep Group Title
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    Yep I understand

    • 2 years ago
  3. pottersheep Group Title
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    I cant get the answer still though

    • 2 years ago
  4. tanjung Group Title
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    change A to (x+y) and B to y

    • 2 years ago
  5. pottersheep Group Title
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    I got it! Ha, it was easier than I thought :)

    • 2 years ago
  6. tanjung Group Title
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    yep, very easy :)

    • 2 years ago
  7. pottersheep Group Title
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    You can have the medal :)

    • 2 years ago
  8. tanjung Group Title
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    thanks, lol

    • 2 years ago
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