Derivative of sin2x-sinx

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

   1. Let $u = 2 x$.

   2. The derivative of sine is cosine:

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

   3. Then, apply the chain rule. Multiply by $\frac{d}{d x} 2 x$:

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

         1. Apply the power rule: $x$ goes to $1$

         So, the result is: $2$

      The result of the chain rule is:

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

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

      1. The derivative of sine is cosine:

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

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

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

The answer is:

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