Integraal van $$$\sin{\left(7 x \right)}$$$

Bepaal $$$\int \sin{\left(7 x \right)}\, dx$$$.

Zij $$$u=7 x$$$.

Dan $$$du=\left(7 x\right)^{\prime }dx = 7 dx$$$ (de stappen zijn te zien »), en dan geldt dat $$$dx = \frac{du}{7}$$$.

De integraal kan worden herschreven als

$${\color{red}{\int{\sin{\left(7 x \right)} d x}}} = {\color{red}{\int{\frac{\sin{\left(u \right)}}{7} d u}}}$$

Pas de constante-veelvoudregel $$$\int c f{\left(u \right)}\, du = c \int f{\left(u \right)}\, du$$$ toe met $$$c=\frac{1}{7}$$$ en $$$f{\left(u \right)} = \sin{\left(u \right)}$$$:

$${\color{red}{\int{\frac{\sin{\left(u \right)}}{7} d u}}} = {\color{red}{\left(\frac{\int{\sin{\left(u \right)} d u}}{7}\right)}}$$

De integraal van de sinus is $$$\int{\sin{\left(u \right)} d u} = - \cos{\left(u \right)}$$$:

$$\frac{{\color{red}{\int{\sin{\left(u \right)} d u}}}}{7} = \frac{{\color{red}{\left(- \cos{\left(u \right)}\right)}}}{7}$$

We herinneren eraan dat $$$u=7 x$$$:

$$- \frac{\cos{\left({\color{red}{u}} \right)}}{7} = - \frac{\cos{\left({\color{red}{\left(7 x\right)}} \right)}}{7}$$

Dus,

$$\int{\sin{\left(7 x \right)} d x} = - \frac{\cos{\left(7 x \right)}}{7}$$

Voeg de integratieconstante toe:

$$\int{\sin{\left(7 x \right)} d x} = - \frac{\cos{\left(7 x \right)}}{7}+C$$

$$$\int \sin{\left(7 x \right)}\, dx = - \frac{\cos{\left(7 x \right)}}{7} + C$$$A