Derivative of sinx-(1/4)*(sin(2x))

1. Differentiate $\sin{\left(x \right)} - \frac{\sin{\left(2 x \right)}}{4}$ term by term:

   1. The derivative of sine is cosine:

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

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

      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:

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

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

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

The answer is:

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