Sunday, 1 June 2014

calculus - How to derive fracddxleft(x+1right)sinleft(xright)



I need help to find derivative of: ddx(x+1)sinx



i tried to do something like this..




(x+1)sinxln(x+1)=sinx(x+1)sin(x)1ln(x+1)(x+1)sin(x)1x+1=sinx(x+1)sin(x)1ln(x+1)(x+1)sinxx+1



I tried another way:



(x+1)sinx=ln(x+1)sinx=sin(x)ln(x+1)=cosln(x+1)+sin(x)1x+1=cos(x)ln(x+1)+sin(x)x+1



ok i got the solution! I put it there, maybe this will help someone!



i used this rule : ea=ealne




(x+1)sinx=esinxln(x+1)=esinxln(x+1)cosxln(x+1)+sinx1x+1=(x+1)(cosxln(x+1)+sinxx+1)


Answer



You have:



f(x)=(x+1)sinx, so lnf=sinxln(x+1). Now we have:



ddxlnf=1fdfdx=ddx[sinxln(x+1)].



You can now solve for f once you expand the LHS of the equation.




Cheers!


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