Mister Exam

Derivative of cos2x*lnx

Function f() - derivative -N order at the point
v

The graph:

from to

Piecewise:

The solution

You have entered [src]
cos(2*x)*log(x)
$$\log{\left(x \right)} \cos{\left(2 x \right)}$$
d                  
--(cos(2*x)*log(x))
dx                 
$$\frac{d}{d x} \log{\left(x \right)} \cos{\left(2 x \right)}$$
Detail solution
  1. Apply the product rule:

    ; to find :

    1. Let .

    2. The derivative of cosine is negative sine:

    3. Then, apply the chain rule. Multiply by :

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

        1. Apply the power rule: goes to

        So, the result is:

      The result of the chain rule is:

    ; to find :

    1. The derivative of is .

    The result is:


The answer is:

The graph
The first derivative [src]
cos(2*x)                    
-------- - 2*log(x)*sin(2*x)
   x                        
$$- 2 \log{\left(x \right)} \sin{\left(2 x \right)} + \frac{\cos{\left(2 x \right)}}{x}$$
The second derivative [src]
 /cos(2*x)   4*sin(2*x)                    \
-|-------- + ---------- + 4*cos(2*x)*log(x)|
 |    2          x                         |
 \   x                                     /
$$- (4 \log{\left(x \right)} \cos{\left(2 x \right)} + \frac{4 \sin{\left(2 x \right)}}{x} + \frac{\cos{\left(2 x \right)}}{x^{2}})$$
The third derivative [src]
  /cos(2*x)   6*cos(2*x)   3*sin(2*x)                    \
2*|-------- - ---------- + ---------- + 4*log(x)*sin(2*x)|
  |    3          x             2                        |
  \   x                        x                         /
$$2 \cdot \left(4 \log{\left(x \right)} \sin{\left(2 x \right)} - \frac{6 \cos{\left(2 x \right)}}{x} + \frac{3 \sin{\left(2 x \right)}}{x^{2}} + \frac{\cos{\left(2 x \right)}}{x^{3}}\right)$$
The graph
Derivative of cos2x*lnx