Mister Exam

Derivative of log3(x)*sin2x

Function f() - derivative -N order at the point
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The graph:

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Piecewise:

The solution

You have entered [src]
log(x)         
------*sin(2*x)
log(3)         
log(x)log(3)sin(2x)\frac{\log{\left(x \right)}}{\log{\left(3 \right)}} \sin{\left(2 x \right)}
(log(x)/log(3))*sin(2*x)
Detail solution
  1. Apply the quotient rule, which is:

    ddxf(x)g(x)=f(x)ddxg(x)+g(x)ddxf(x)g2(x)\frac{d}{d x} \frac{f{\left(x \right)}}{g{\left(x \right)}} = \frac{- f{\left(x \right)} \frac{d}{d x} g{\left(x \right)} + g{\left(x \right)} \frac{d}{d x} f{\left(x \right)}}{g^{2}{\left(x \right)}}

    f(x)=log(x)sin(2x)f{\left(x \right)} = \log{\left(x \right)} \sin{\left(2 x \right)} and g(x)=log(3)g{\left(x \right)} = \log{\left(3 \right)}.

    To find ddxf(x)\frac{d}{d x} f{\left(x \right)}:

    1. Apply the product rule:

      ddxf(x)g(x)=f(x)ddxg(x)+g(x)ddxf(x)\frac{d}{d x} f{\left(x \right)} g{\left(x \right)} = f{\left(x \right)} \frac{d}{d x} g{\left(x \right)} + g{\left(x \right)} \frac{d}{d x} f{\left(x \right)}

      f(x)=log(x)f{\left(x \right)} = \log{\left(x \right)}; to find ddxf(x)\frac{d}{d x} f{\left(x \right)}:

      1. The derivative of log(x)\log{\left(x \right)} is 1x\frac{1}{x}.

      g(x)=sin(2x)g{\left(x \right)} = \sin{\left(2 x \right)}; to find ddxg(x)\frac{d}{d x} g{\left(x \right)}:

      1. Let u=2xu = 2 x.

      2. The derivative of sine is cosine:

        ddusin(u)=cos(u)\frac{d}{d u} \sin{\left(u \right)} = \cos{\left(u \right)}

      3. Then, apply the chain rule. Multiply by ddx2x\frac{d}{d x} 2 x:

        1. The derivative of a constant times a function is the constant times the derivative of the function.

          1. Apply the power rule: xx goes to 11

          So, the result is: 22

        The result of the chain rule is:

        2cos(2x)2 \cos{\left(2 x \right)}

      The result is: 2log(x)cos(2x)+sin(2x)x2 \log{\left(x \right)} \cos{\left(2 x \right)} + \frac{\sin{\left(2 x \right)}}{x}

    To find ddxg(x)\frac{d}{d x} g{\left(x \right)}:

    1. The derivative of the constant log(3)\log{\left(3 \right)} is zero.

    Now plug in to the quotient rule:

    2log(x)cos(2x)+sin(2x)xlog(3)\frac{2 \log{\left(x \right)} \cos{\left(2 x \right)} + \frac{\sin{\left(2 x \right)}}{x}}{\log{\left(3 \right)}}

  2. Now simplify:

    2xlog(x)cos(2x)+sin(2x)xlog(3)\frac{2 x \log{\left(x \right)} \cos{\left(2 x \right)} + \sin{\left(2 x \right)}}{x \log{\left(3 \right)}}


The answer is:

2xlog(x)cos(2x)+sin(2x)xlog(3)\frac{2 x \log{\left(x \right)} \cos{\left(2 x \right)} + \sin{\left(2 x \right)}}{x \log{\left(3 \right)}}

The graph
02468-8-6-4-2-1010-1010
The first derivative [src]
sin(2*x)   2*cos(2*x)*log(x)
-------- + -----------------
x*log(3)         log(3)     
2log(x)cos(2x)log(3)+sin(2x)xlog(3)\frac{2 \log{\left(x \right)} \cos{\left(2 x \right)}}{\log{\left(3 \right)}} + \frac{\sin{\left(2 x \right)}}{x \log{\left(3 \right)}}
The second derivative [src]
  sin(2*x)                       4*cos(2*x)
- -------- - 4*log(x)*sin(2*x) + ----------
      2                              x     
     x                                     
-------------------------------------------
                   log(3)                  
4log(x)sin(2x)+4cos(2x)xsin(2x)x2log(3)\frac{- 4 \log{\left(x \right)} \sin{\left(2 x \right)} + \frac{4 \cos{\left(2 x \right)}}{x} - \frac{\sin{\left(2 x \right)}}{x^{2}}}{\log{\left(3 \right)}}
The third derivative [src]
  /sin(2*x)   6*sin(2*x)                       3*cos(2*x)\
2*|-------- - ---------- - 4*cos(2*x)*log(x) - ----------|
  |    3          x                                 2    |
  \   x                                            x     /
----------------------------------------------------------
                          log(3)                          
2(4log(x)cos(2x)6sin(2x)x3cos(2x)x2+sin(2x)x3)log(3)\frac{2 \left(- 4 \log{\left(x \right)} \cos{\left(2 x \right)} - \frac{6 \sin{\left(2 x \right)}}{x} - \frac{3 \cos{\left(2 x \right)}}{x^{2}} + \frac{\sin{\left(2 x \right)}}{x^{3}}\right)}{\log{\left(3 \right)}}