Integral of $$$\cos{\left(23 x \right)}$$$

Find $$$\int \cos{\left(23 x \right)}\, dx$$$.

Let $$$u=23 x$$$.

Then $$$du=\left(23 x\right)^{\prime }dx = 23 dx$$$ (steps can be seen »), and we have that $$$dx = \frac{du}{23}$$$.

The integral becomes

$${\color{red}{\int{\cos{\left(23 x \right)} d x}}} = {\color{red}{\int{\frac{\cos{\left(u \right)}}{23} d u}}}$$

Apply the constant multiple rule $$$\int c f{\left(u \right)}\, du = c \int f{\left(u \right)}\, du$$$ with $$$c=\frac{1}{23}$$$ and $$$f{\left(u \right)} = \cos{\left(u \right)}$$$:

$${\color{red}{\int{\frac{\cos{\left(u \right)}}{23} d u}}} = {\color{red}{\left(\frac{\int{\cos{\left(u \right)} d u}}{23}\right)}}$$

The integral of the cosine is $$$\int{\cos{\left(u \right)} d u} = \sin{\left(u \right)}$$$:

$$\frac{{\color{red}{\int{\cos{\left(u \right)} d u}}}}{23} = \frac{{\color{red}{\sin{\left(u \right)}}}}{23}$$

Recall that $$$u=23 x$$$:

$$\frac{\sin{\left({\color{red}{u}} \right)}}{23} = \frac{\sin{\left({\color{red}{\left(23 x\right)}} \right)}}{23}$$

Therefore,

$$\int{\cos{\left(23 x \right)} d x} = \frac{\sin{\left(23 x \right)}}{23}$$

Add the constant of integration:

$$\int{\cos{\left(23 x \right)} d x} = \frac{\sin{\left(23 x \right)}}{23}+C$$

$$$\int \cos{\left(23 x \right)}\, dx = \frac{\sin{\left(23 x \right)}}{23} + C$$$A