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log(sin(x/2))-cot(x/2)

Derivative of log(sin(x/2))-cot(x/2)

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   /   /x\\      /x\
log|sin|-|| - cot|-|
   \   \2//      \2/
log(sin(x2))cot(x2)\log{\left(\sin{\left(\frac{x}{2} \right)} \right)} - \cot{\left(\frac{x}{2} \right)}
log(sin(x/2)) - cot(x/2)
Detail solution
  1. Differentiate log(sin(x2))cot(x2)\log{\left(\sin{\left(\frac{x}{2} \right)} \right)} - \cot{\left(\frac{x}{2} \right)} term by term:

    1. Let u=sin(x2)u = \sin{\left(\frac{x}{2} \right)}.

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

    3. Then, apply the chain rule. Multiply by ddxsin(x2)\frac{d}{d x} \sin{\left(\frac{x}{2} \right)}:

      1. Let u=x2u = \frac{x}{2}.

      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 ddxx2\frac{d}{d x} \frac{x}{2}:

        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: 12\frac{1}{2}

        The result of the chain rule is:

        cos(x2)2\frac{\cos{\left(\frac{x}{2} \right)}}{2}

      The result of the chain rule is:

      cos(x2)2sin(x2)\frac{\cos{\left(\frac{x}{2} \right)}}{2 \sin{\left(\frac{x}{2} \right)}}

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

      1. There are multiple ways to do this derivative.

        Method #1

        1. Rewrite the function to be differentiated:

          cot(x2)=1tan(x2)\cot{\left(\frac{x}{2} \right)} = \frac{1}{\tan{\left(\frac{x}{2} \right)}}

        2. Let u=tan(x2)u = \tan{\left(\frac{x}{2} \right)}.

        3. Apply the power rule: 1u\frac{1}{u} goes to 1u2- \frac{1}{u^{2}}

        4. Then, apply the chain rule. Multiply by ddxtan(x2)\frac{d}{d x} \tan{\left(\frac{x}{2} \right)}:

          1. Rewrite the function to be differentiated:

            tan(x2)=sin(x2)cos(x2)\tan{\left(\frac{x}{2} \right)} = \frac{\sin{\left(\frac{x}{2} \right)}}{\cos{\left(\frac{x}{2} \right)}}

          2. 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)=sin(x2)f{\left(x \right)} = \sin{\left(\frac{x}{2} \right)} and g(x)=cos(x2)g{\left(x \right)} = \cos{\left(\frac{x}{2} \right)}.

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

            1. Let u=x2u = \frac{x}{2}.

            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 ddxx2\frac{d}{d x} \frac{x}{2}:

              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: 12\frac{1}{2}

              The result of the chain rule is:

              cos(x2)2\frac{\cos{\left(\frac{x}{2} \right)}}{2}

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

            1. Let u=x2u = \frac{x}{2}.

            2. The derivative of cosine is negative sine:

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

            3. Then, apply the chain rule. Multiply by ddxx2\frac{d}{d x} \frac{x}{2}:

              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: 12\frac{1}{2}

              The result of the chain rule is:

              sin(x2)2- \frac{\sin{\left(\frac{x}{2} \right)}}{2}

            Now plug in to the quotient rule:

            sin2(x2)2+cos2(x2)2cos2(x2)\frac{\frac{\sin^{2}{\left(\frac{x}{2} \right)}}{2} + \frac{\cos^{2}{\left(\frac{x}{2} \right)}}{2}}{\cos^{2}{\left(\frac{x}{2} \right)}}

          The result of the chain rule is:

          sin2(x2)2+cos2(x2)2cos2(x2)tan2(x2)- \frac{\frac{\sin^{2}{\left(\frac{x}{2} \right)}}{2} + \frac{\cos^{2}{\left(\frac{x}{2} \right)}}{2}}{\cos^{2}{\left(\frac{x}{2} \right)} \tan^{2}{\left(\frac{x}{2} \right)}}

        Method #2

        1. Rewrite the function to be differentiated:

          cot(x2)=cos(x2)sin(x2)\cot{\left(\frac{x}{2} \right)} = \frac{\cos{\left(\frac{x}{2} \right)}}{\sin{\left(\frac{x}{2} \right)}}

        2. 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)=cos(x2)f{\left(x \right)} = \cos{\left(\frac{x}{2} \right)} and g(x)=sin(x2)g{\left(x \right)} = \sin{\left(\frac{x}{2} \right)}.

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

          1. Let u=x2u = \frac{x}{2}.

          2. The derivative of cosine is negative sine:

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

          3. Then, apply the chain rule. Multiply by ddxx2\frac{d}{d x} \frac{x}{2}:

            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: 12\frac{1}{2}

            The result of the chain rule is:

            sin(x2)2- \frac{\sin{\left(\frac{x}{2} \right)}}{2}

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

          1. Let u=x2u = \frac{x}{2}.

          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 ddxx2\frac{d}{d x} \frac{x}{2}:

            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: 12\frac{1}{2}

            The result of the chain rule is:

            cos(x2)2\frac{\cos{\left(\frac{x}{2} \right)}}{2}

          Now plug in to the quotient rule:

          sin2(x2)2cos2(x2)2sin2(x2)\frac{- \frac{\sin^{2}{\left(\frac{x}{2} \right)}}{2} - \frac{\cos^{2}{\left(\frac{x}{2} \right)}}{2}}{\sin^{2}{\left(\frac{x}{2} \right)}}

      So, the result is: sin2(x2)2+cos2(x2)2cos2(x2)tan2(x2)\frac{\frac{\sin^{2}{\left(\frac{x}{2} \right)}}{2} + \frac{\cos^{2}{\left(\frac{x}{2} \right)}}{2}}{\cos^{2}{\left(\frac{x}{2} \right)} \tan^{2}{\left(\frac{x}{2} \right)}}

    The result is: sin2(x2)2+cos2(x2)2cos2(x2)tan2(x2)+cos(x2)2sin(x2)\frac{\frac{\sin^{2}{\left(\frac{x}{2} \right)}}{2} + \frac{\cos^{2}{\left(\frac{x}{2} \right)}}{2}}{\cos^{2}{\left(\frac{x}{2} \right)} \tan^{2}{\left(\frac{x}{2} \right)}} + \frac{\cos{\left(\frac{x}{2} \right)}}{2 \sin{\left(\frac{x}{2} \right)}}

  2. Now simplify:

    sin(x)2+1(cos(x)+1)tan2(x2)\frac{\frac{\sin{\left(x \right)}}{2} + 1}{\left(\cos{\left(x \right)} + 1\right) \tan^{2}{\left(\frac{x}{2} \right)}}


The answer is:

sin(x)2+1(cos(x)+1)tan2(x2)\frac{\frac{\sin{\left(x \right)}}{2} + 1}{\left(\cos{\left(x \right)} + 1\right) \tan^{2}{\left(\frac{x}{2} \right)}}

The graph
02468-8-6-4-2-1010-500500
The first derivative [src]
       2/x\       /x\ 
    cot |-|    cos|-| 
1       \2/       \2/ 
- + ------- + --------
2      2           /x\
              2*sin|-|
                   \2/
cot2(x2)2+12+cos(x2)2sin(x2)\frac{\cot^{2}{\left(\frac{x}{2} \right)}}{2} + \frac{1}{2} + \frac{\cos{\left(\frac{x}{2} \right)}}{2 \sin{\left(\frac{x}{2} \right)}}
The second derivative [src]
 /       2/x\                         \ 
 |    cos |-|                         | 
 |        \2/     /       2/x\\    /x\| 
-|1 + ------- + 2*|1 + cot |-||*cot|-|| 
 |       2/x\     \        \2//    \2/| 
 |    sin |-|                         | 
 \        \2/                         / 
----------------------------------------
                   4                    
2(cot2(x2)+1)cot(x2)+1+cos2(x2)sin2(x2)4- \frac{2 \left(\cot^{2}{\left(\frac{x}{2} \right)} + 1\right) \cot{\left(\frac{x}{2} \right)} + 1 + \frac{\cos^{2}{\left(\frac{x}{2} \right)}}{\sin^{2}{\left(\frac{x}{2} \right)}}}{4}
The third derivative [src]
                    3/x\      /x\                          
             2   cos |-|   cos|-|                          
/       2/x\\        \2/      \2/        2/x\ /       2/x\\
|1 + cot |-||  + ------- + ------ + 2*cot |-|*|1 + cot |-||
\        \2//       3/x\      /x\         \2/ \        \2//
                 sin |-|   sin|-|                          
                     \2/      \2/                          
-----------------------------------------------------------
                             4                             
(cot2(x2)+1)2+2(cot2(x2)+1)cot2(x2)+cos(x2)sin(x2)+cos3(x2)sin3(x2)4\frac{\left(\cot^{2}{\left(\frac{x}{2} \right)} + 1\right)^{2} + 2 \left(\cot^{2}{\left(\frac{x}{2} \right)} + 1\right) \cot^{2}{\left(\frac{x}{2} \right)} + \frac{\cos{\left(\frac{x}{2} \right)}}{\sin{\left(\frac{x}{2} \right)}} + \frac{\cos^{3}{\left(\frac{x}{2} \right)}}{\sin^{3}{\left(\frac{x}{2} \right)}}}{4}
The graph
Derivative of log(sin(x/2))-cot(x/2)