Integral dari $$$\sin{\left(9 x \right)}$$$

Temukan $$$\int \sin{\left(9 x \right)}\, dx$$$.

Misalkan $$$u=9 x$$$.

Kemudian $$$du=\left(9 x\right)^{\prime }dx = 9 dx$$$ (langkah-langkah dapat dilihat di »), dan kita memperoleh $$$dx = \frac{du}{9}$$$.

Oleh karena itu,

$${\color{red}{\int{\sin{\left(9 x \right)} d x}}} = {\color{red}{\int{\frac{\sin{\left(u \right)}}{9} d u}}}$$

Terapkan aturan pengali konstanta $$$\int c f{\left(u \right)}\, du = c \int f{\left(u \right)}\, du$$$ dengan $$$c=\frac{1}{9}$$$ dan $$$f{\left(u \right)} = \sin{\left(u \right)}$$$:

$${\color{red}{\int{\frac{\sin{\left(u \right)}}{9} d u}}} = {\color{red}{\left(\frac{\int{\sin{\left(u \right)} d u}}{9}\right)}}$$

Integral dari sinus adalah $$$\int{\sin{\left(u \right)} d u} = - \cos{\left(u \right)}$$$:

$$\frac{{\color{red}{\int{\sin{\left(u \right)} d u}}}}{9} = \frac{{\color{red}{\left(- \cos{\left(u \right)}\right)}}}{9}$$

Ingat bahwa $$$u=9 x$$$:

$$- \frac{\cos{\left({\color{red}{u}} \right)}}{9} = - \frac{\cos{\left({\color{red}{\left(9 x\right)}} \right)}}{9}$$

Oleh karena itu,

$$\int{\sin{\left(9 x \right)} d x} = - \frac{\cos{\left(9 x \right)}}{9}$$

Tambahkan konstanta integrasi:

$$\int{\sin{\left(9 x \right)} d x} = - \frac{\cos{\left(9 x \right)}}{9}+C$$

$$$\int \sin{\left(9 x \right)}\, dx = - \frac{\cos{\left(9 x \right)}}{9} + C$$$A