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Math Help - Check my answers for Higher derivatives

  1. #1
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    Exclamation Check my answers for Higher derivatives

    1) find y' if y=2sin2x+5cos3x-4
    Attempt:
     (2)sin(2x)+(5)cos(3x-4)
    =4cos2x-15sin3x-4
    2) find y" if  y=cotx
    Attempt:
    y'= -csc^2x
    y"= 2csc^2xcotx
    3) find y" if  y=x.tanx
    Attempt:
    y'= (x)(sex^2x)+tanx
    y"= (x)(-2sec^2x)tanx+sec^4x
    4)find y" if  3sin^3(2x)
    Attempt;
    y'= 18(sin^2x)(cos2x)
    y"= -36 sin^3 2x+4cos^2 2x sin2x
    5)find y" if  x^5+3x^3+6
    Attempt:
    y'= 5x^4+9x^2
    y"= 20x^3+18x

    Please check is my answer are correct,if not write the correct solution in steps...
    Thank you
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  2. #2
    Senior Member I-Think's Avatar
    Joined
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    You should use this site to check your derivatives

    Wolfram Mathematica Online Integrator

    For no.4 y' should be 18(sin^22x)(cos2x)
    and
    y''=18(2cos^22xsin2x+-2sin^32x)

    No.3
    y'=(x)(sex^2x)+tanx
    y''=2xsec^3xsinx+2sec^2x

    N.B
    \frac{d}{dx}(xsec^2x)=2xsec^3xsinx+sec^2x
    Last edited by I-Think; November 11th 2009 at 05:24 AM.
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  3. #3
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    Quote Originally Posted by I-Think View Post
    You should use this site to check your derivatives

    Wolfram Mathematica Online Integrator

    For no.4 y' should be 18(sin^22x)(cos2x)
    and
    y''=18(2cos^22xsin2x+-2sin^32x)

    No.3
    y'=(x)(sex^2x)+tanx
    y''=2xsec^3xsinx+2sec^2x

    N.B
    \frac{d}{dx}(xsec^2x)=2xsec^3xsinx+sec^2x
    So are there any mistakes ,btw thnx for the site but i am differentiating not integrating
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