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pottersheep

  • 3 years ago

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

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  1. tanjung
    • 3 years ago
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    just to understanding the formula : cosAcosB + sinAsinB = cos(A-B)

  2. pottersheep
    • 3 years ago
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    Yep I understand

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

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

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

  6. tanjung
    • 3 years ago
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    yep, very easy :)

  7. pottersheep
    • 3 years ago
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    You can have the medal :)

  8. tanjung
    • 3 years ago
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    thanks, lol

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