Mister Exam

Derivative of y=ctg(x)+sqrt(x)

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

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           ___
cot(x) + \/ x 
x+cot(x)\sqrt{x} + \cot{\left(x \right)}
d /           ___\
--\cot(x) + \/ x /
dx                
ddx(x+cot(x))\frac{d}{d x} \left(\sqrt{x} + \cot{\left(x \right)}\right)
Detail solution
  1. Differentiate x+cot(x)\sqrt{x} + \cot{\left(x \right)} term by term:

    1. 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. 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)}}

        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)}}

    2. Apply the power rule: x\sqrt{x} goes to 12x\frac{1}{2 \sqrt{x}}

    The result is: sin2(x)+cos2(x)cos2(x)tan2(x)+12x- \frac{\sin^{2}{\left(x \right)} + \cos^{2}{\left(x \right)}}{\cos^{2}{\left(x \right)} \tan^{2}{\left(x \right)}} + \frac{1}{2 \sqrt{x}}

  2. Now simplify:

    1sin2(x)+12x- \frac{1}{\sin^{2}{\left(x \right)}} + \frac{1}{2 \sqrt{x}}


The answer is:

1sin2(x)+12x- \frac{1}{\sin^{2}{\left(x \right)}} + \frac{1}{2 \sqrt{x}}

The graph
02468-8-6-4-2-1010-1000010000
The first derivative [src]
        1         2   
-1 + ------- - cot (x)
         ___          
     2*\/ x           
cot2(x)1+12x- \cot^{2}{\left(x \right)} - 1 + \frac{1}{2 \sqrt{x}}
The second derivative [src]
    1        /       2   \       
- ------ + 2*\1 + cot (x)/*cot(x)
     3/2                         
  4*x                            
2(cot2(x)+1)cot(x)14x322 \left(\cot^{2}{\left(x \right)} + 1\right) \cot{\left(x \right)} - \frac{1}{4 x^{\frac{3}{2}}}
The third derivative [src]
                 2                                   
    /       2   \      3           2    /       2   \
- 2*\1 + cot (x)/  + ------ - 4*cot (x)*\1 + cot (x)/
                        5/2                          
                     8*x                             
2(cot2(x)+1)24(cot2(x)+1)cot2(x)+38x52- 2 \left(\cot^{2}{\left(x \right)} + 1\right)^{2} - 4 \left(\cot^{2}{\left(x \right)} + 1\right) \cot^{2}{\left(x \right)} + \frac{3}{8 x^{\frac{5}{2}}}
The graph
Derivative of y=ctg(x)+sqrt(x)