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Math Help - trig function differenciation

  1. #1
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    trig function differenciation

    if y= 3sin(2x+3) show that y"+4y=0

    and

    if y= sinx + 2cosx show that y", + y""+y, +y =O

    can some1 explain to me how to do these and solve them

    k thnx
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  2. #2
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    Re: trig function differenciation

    What is y'',Can you explain?
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  3. #3
    GJA
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    Re: trig function differenciation

    Hi, srirahulan. To answer your question, y'' is the second derivative of the function we are considering - in this case y=3sin(2x+3).
    Last edited by GJA; August 5th 2012 at 09:51 PM.
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  4. #4
    GJA
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    Re: trig function differenciation

    Hi, arsenal12345. What we need to do is compute the second derivative y'' of y=3sin(2x+3) first. Then add 4y to what we get and see if it does equal zero. Does this answer your question? Good luck!
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  5. #5
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    Re: trig function differenciation

    man i dont get it i am as lost as a nube can get
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  6. #6
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    Re: trig function differenciation

    What GJA is saying, find y'' given that y = 3 \sin (2x + 3). Does y'' + 4y always equal zero?
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  7. #7
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    Re: trig function differenciation

    no
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  8. #8
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    Re: trig function differenciation

    Are you sure?
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  9. #9
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    Re: trig function differenciation

    no not sure, can u please solve it and explain to me how u got ur answear ?
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  10. #10
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    Re: trig function differenciation

    Quote Originally Posted by arsenal12345 View Post
    if y= 3sin(2x+3) show that y"+4y=0

    and

    if y= sinx + 2cosx show that y", + y""+y, +y =O

    can some1 explain to me how to do these and solve them

    k thnx
    For the first one:

     y'=6\cos(2x+3)
     y'' = -12\sin(2x+3)

    Therefore... LHS=y''+4y=-12\sin(2x+3)+4(3sin(2x+3))=0=RHS

    Do the same for the second one
    Thanks from arsenal12345
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