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1018

  • one year ago

for y=4sin(3x), find y(pi)

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  1. welshfella
    • one year ago
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    plug in pi for x

  2. 1018
    • one year ago
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    oh wait sorry that's supposed to be y'(pi)

  3. welshfella
    • one year ago
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    ok so you have to find the derivative of 4 sin3x

  4. 1018
    • one year ago
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    oh wait i think i got it can you check if this is right

  5. welshfella
    • one year ago
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    ok

  6. 1018
    • one year ago
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    y'=4cos(3x)(3) ?

  7. welshfella
    • one year ago
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    yea or you could write it as 12 cos (3x)

  8. 1018
    • one year ago
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    thanks! may i ask, is this always the right way, because at first i thought i would use the chain rule on 4 and sin(3x)

  9. welshfella
    • one year ago
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    sin (3x) is a compound function Ignore the 4 at first - just use chain rule on sin 3x . Finally multiply the result by 4.

  10. 1018
    • one year ago
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    oh, so should i just ignore numbers that appears before the trig function? i should just do what's inside the funtion?

  11. welshfella
    • one year ago
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    yes - but of course dont forget to operate on them after you have done the differentiation

  12. welshfella
    • one year ago
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    eg 2 cos 3x = 2 * -3sin 3x = -6 sin 3x

  13. 1018
    • one year ago
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    yes, thanks! oh wait, last one, may you answer this? i think the answer is 0 but not sure

  14. 1018
    • one year ago
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    y=1-2u u = x^3 - 2x^2 + 6 find y''(x=1)

  15. welshfella
    • one year ago
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    y = 1 - 2(x^3 - 2x^2 + 6) y = 1 - 2x^3 + 4x^2 - 12 what do you get for y' ?

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