Mister Exam

Derivative of ln(tgx+ctgx)/(sina)

Function f() - derivative -N order at the point
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log(tan(x) + cot(x))
--------------------
       sin(a)       
log(tan(x)+cot(x))sin(a)\frac{\log{\left(\tan{\left(x \right)} + \cot{\left(x \right)} \right)}}{\sin{\left(a \right)}}
log(tan(x) + cot(x))/sin(a)
Detail solution
  1. The derivative of a constant times a function is the constant times the derivative of the function.

    1. Let u=tan(x)+cot(x)u = \tan{\left(x \right)} + \cot{\left(x \right)}.

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

    3. Then, apply the chain rule. Multiply by ddx(tan(x)+cot(x))\frac{d}{d x} \left(\tan{\left(x \right)} + \cot{\left(x \right)}\right):

      1. Differentiate tan(x)+cot(x)\tan{\left(x \right)} + \cot{\left(x \right)} term by term:

        1. Rewrite the function to be differentiated:

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

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

          1. The derivative of sine is cosine:

            ddxsin(x)=cos(x)\frac{d}{d x} \sin{\left(x \right)} = \cos{\left(x \right)}

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

          1. The derivative of cosine is negative sine:

            ddxcos(x)=sin(x)\frac{d}{d x} \cos{\left(x \right)} = - \sin{\left(x \right)}

          Now plug in to the quotient rule:

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

        3. There are multiple ways to do this derivative.

          Method #1

          1. Rewrite the function to be differentiated:

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

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

            1. ddxtan(x)=1cos2(x)\frac{d}{d x} \tan{\left(x \right)} = \frac{1}{\cos^{2}{\left(x \right)}}

            The result of the chain rule is:

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

          Method #2

          1. Rewrite the function to be differentiated:

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

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

            1. The derivative of cosine is negative sine:

              ddxcos(x)=sin(x)\frac{d}{d x} \cos{\left(x \right)} = - \sin{\left(x \right)}

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

            1. The derivative of sine is cosine:

              ddxsin(x)=cos(x)\frac{d}{d x} \sin{\left(x \right)} = \cos{\left(x \right)}

            Now plug in to the quotient rule:

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

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

      The result of the chain rule is:

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

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

  2. Now simplify:

    tan(x)1tan(x)sin(a)\frac{\tan{\left(x \right)} - \frac{1}{\tan{\left(x \right)}}}{\sin{\left(a \right)}}


The answer is:

tan(x)1tan(x)sin(a)\frac{\tan{\left(x \right)} - \frac{1}{\tan{\left(x \right)}}}{\sin{\left(a \right)}}

The first derivative [src]
      2         2       
   tan (x) - cot (x)    
------------------------
(tan(x) + cot(x))*sin(a)
tan2(x)cot2(x)(tan(x)+cot(x))sin(a)\frac{\tan^{2}{\left(x \right)} - \cot^{2}{\left(x \right)}}{\left(\tan{\left(x \right)} + \cot{\left(x \right)}\right) \sin{\left(a \right)}}
The second derivative [src]
                     2                                                  
  /   2         2   \                                                   
  \tan (x) - cot (x)/      /       2   \            /       2   \       
- -------------------- + 2*\1 + cot (x)/*cot(x) + 2*\1 + tan (x)/*tan(x)
    cot(x) + tan(x)                                                     
------------------------------------------------------------------------
                        (cot(x) + tan(x))*sin(a)                        
2(tan2(x)+1)tan(x)+2(cot2(x)+1)cot(x)(tan2(x)cot2(x))2tan(x)+cot(x)(tan(x)+cot(x))sin(a)\frac{2 \left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} + 2 \left(\cot^{2}{\left(x \right)} + 1\right) \cot{\left(x \right)} - \frac{\left(\tan^{2}{\left(x \right)} - \cot^{2}{\left(x \right)}\right)^{2}}{\tan{\left(x \right)} + \cot{\left(x \right)}}}{\left(\tan{\left(x \right)} + \cot{\left(x \right)}\right) \sin{\left(a \right)}}
The third derivative [src]
   /                                                     3                                                                                                                          \
   |             2                2   /   2         2   \                                                          /   2         2   \ //       2   \          /       2   \       \|
   |/       2   \    /       2   \    \tan (x) - cot (x)/         2    /       2   \        2    /       2   \   3*\tan (x) - cot (x)/*\\1 + cot (x)/*cot(x) + \1 + tan (x)/*tan(x)/|
-2*|\1 + cot (x)/  - \1 + tan (x)/  - -------------------- - 2*tan (x)*\1 + tan (x)/ + 2*cot (x)*\1 + cot (x)/ + -------------------------------------------------------------------|
   |                                                    2                                                                                  cot(x) + tan(x)                          |
   \                                   (cot(x) + tan(x))                                                                                                                            /
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               (cot(x) + tan(x))*sin(a)                                                                              
2(3((tan2(x)+1)tan(x)+(cot2(x)+1)cot(x))(tan2(x)cot2(x))tan(x)+cot(x)(tan2(x)+1)22(tan2(x)+1)tan2(x)+(cot2(x)+1)2+2(cot2(x)+1)cot2(x)(tan2(x)cot2(x))3(tan(x)+cot(x))2)(tan(x)+cot(x))sin(a)- \frac{2 \left(\frac{3 \left(\left(\tan^{2}{\left(x \right)} + 1\right) \tan{\left(x \right)} + \left(\cot^{2}{\left(x \right)} + 1\right) \cot{\left(x \right)}\right) \left(\tan^{2}{\left(x \right)} - \cot^{2}{\left(x \right)}\right)}{\tan{\left(x \right)} + \cot{\left(x \right)}} - \left(\tan^{2}{\left(x \right)} + 1\right)^{2} - 2 \left(\tan^{2}{\left(x \right)} + 1\right) \tan^{2}{\left(x \right)} + \left(\cot^{2}{\left(x \right)} + 1\right)^{2} + 2 \left(\cot^{2}{\left(x \right)} + 1\right) \cot^{2}{\left(x \right)} - \frac{\left(\tan^{2}{\left(x \right)} - \cot^{2}{\left(x \right)}\right)^{3}}{\left(\tan{\left(x \right)} + \cot{\left(x \right)}\right)^{2}}\right)}{\left(\tan{\left(x \right)} + \cot{\left(x \right)}\right) \sin{\left(a \right)}}