Mister Exam

Derivative of ysin(y)^2

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

from to

Piecewise:

The solution

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     2   
y*sin (y)
ysin2(y)y \sin^{2}{\left(y \right)}
d /     2   \
--\y*sin (y)/
dy           
ddyysin2(y)\frac{d}{d y} y \sin^{2}{\left(y \right)}
Detail solution
  1. Apply the product rule:

    ddyf(y)g(y)=f(y)ddyg(y)+g(y)ddyf(y)\frac{d}{d y} f{\left(y \right)} g{\left(y \right)} = f{\left(y \right)} \frac{d}{d y} g{\left(y \right)} + g{\left(y \right)} \frac{d}{d y} f{\left(y \right)}

    f(y)=yf{\left(y \right)} = y; to find ddyf(y)\frac{d}{d y} f{\left(y \right)}:

    1. Apply the power rule: yy goes to 11

    g(y)=sin2(y)g{\left(y \right)} = \sin^{2}{\left(y \right)}; to find ddyg(y)\frac{d}{d y} g{\left(y \right)}:

    1. Let u=sin(y)u = \sin{\left(y \right)}.

    2. Apply the power rule: u2u^{2} goes to 2u2 u

    3. Then, apply the chain rule. Multiply by ddysin(y)\frac{d}{d y} \sin{\left(y \right)}:

      1. The derivative of sine is cosine:

        ddysin(y)=cos(y)\frac{d}{d y} \sin{\left(y \right)} = \cos{\left(y \right)}

      The result of the chain rule is:

      2sin(y)cos(y)2 \sin{\left(y \right)} \cos{\left(y \right)}

    The result is: 2ysin(y)cos(y)+sin2(y)2 y \sin{\left(y \right)} \cos{\left(y \right)} + \sin^{2}{\left(y \right)}

  2. Now simplify:

    ysin(2y)cos(2y)2+12y \sin{\left(2 y \right)} - \frac{\cos{\left(2 y \right)}}{2} + \frac{1}{2}


The answer is:

ysin(2y)cos(2y)2+12y \sin{\left(2 y \right)} - \frac{\cos{\left(2 y \right)}}{2} + \frac{1}{2}

The graph
02468-8-6-4-2-1010-2020
The first derivative [src]
   2                       
sin (y) + 2*y*cos(y)*sin(y)
2ysin(y)cos(y)+sin2(y)2 y \sin{\left(y \right)} \cos{\left(y \right)} + \sin^{2}{\left(y \right)}
The second derivative [src]
  /    /   2         2   \                  \
2*\- y*\sin (y) - cos (y)/ + 2*cos(y)*sin(y)/
2(y(sin2(y)cos2(y))+2sin(y)cos(y))2 \left(- y \left(\sin^{2}{\left(y \right)} - \cos^{2}{\left(y \right)}\right) + 2 \sin{\left(y \right)} \cos{\left(y \right)}\right)
The third derivative [src]
  /       2           2                       \
2*\- 3*sin (y) + 3*cos (y) - 4*y*cos(y)*sin(y)/
2(4ysin(y)cos(y)3sin2(y)+3cos2(y))2 \left(- 4 y \sin{\left(y \right)} \cos{\left(y \right)} - 3 \sin^{2}{\left(y \right)} + 3 \cos^{2}{\left(y \right)}\right)
The graph
Derivative of ysin(y)^2