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sara1234

  • 3 years ago

Helpp

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  1. sara1234
    • 3 years ago
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    @jim_thompson5910 @Nameless

  2. jim_thompson5910
    • 3 years ago
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    sin(3x) = sin(2x + x) sin(3x) = sin(2x)cos(x) + cos(2x)sin(x) sin(3x) = sin(x+x)cos(x) + cos(x+x)sin(x) sin(3x) = [sin(x)cos(x) + cos(x)sin(x)]cos(x) + [cos(x)cos(x) - sin(x)sin(x)]sin(x) sin(3x) = [2cos(x)sin(x)]cos(x) + [cos^2(x) - sin^2(x)]sin(x) sin(3x) = 2cos^2(x)sin(x) + cos^2(x)sin(x) - sin^3(x) Do the same to find cos(3x)

  3. jim_thompson5910
    • 3 years ago
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    I'm using the identities sin(x+y) = sin(x)cos(y) + cos(x)sin(y) cos(x+y) = cos(x)cos(y) - sin(x)sin(y)

  4. jim_thompson5910
    • 3 years ago
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    sry i should have gone further sin(3x) = 3cos^2(x)sin(x) - sin^3(x)

  5. sara1234
    • 3 years ago
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    im confused can you tell me what the answer is so i can check if i got it right?

  6. jim_thompson5910
    • 3 years ago
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    hold on one sec

  7. jim_thompson5910
    • 3 years ago
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    checking the answer, but the second one doesn't seem right, but one sec

  8. sara1234
    • 3 years ago
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    ok thank you

  9. jim_thompson5910
    • 3 years ago
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    well using a graphing calculator, I was able to eliminate choices A through C so that leaves D

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