Derivative of (7+2*cos(x))*sin(x)

1. Apply the product rule:

   $$\frac{d}{d x} f{\left(x \right)} g{\left(x \right)} = f{\left(x \right)} \frac{d}{d x} g{\left(x \right)} + g{\left(x \right)} \frac{d}{d x} f{\left(x \right)}$$

   $f{\left(x \right)} = 2 \cos{\left(x \right)} + 7$; to find $\frac{d}{d x} f{\left(x \right)}$:

   1. Differentiate $2 \cos{\left(x \right)} + 7$ term by term:

      1. The derivative of the constant $7$ is zero.

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

         1. The derivative of cosine is negative sine:

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

         So, the result is: $- 2 \sin{\left(x \right)}$

      The result is: $- 2 \sin{\left(x \right)}$

   $g{\left(x \right)} = \sin{\left(x \right)}$; to find $\frac{d}{d x} g{\left(x \right)}$:

   1. The derivative of sine is cosine:

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

   The result is: $\left(2 \cos{\left(x \right)} + 7\right) \cos{\left(x \right)} - 2 \sin^{2}{\left(x \right)}$

2. Now simplify:

   $$7 \cos{\left(x \right)} + 2 \cos{\left(2 x \right)}$$

The answer is: