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

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

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

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

Deze integraal (Sinusintegraal) heeft geen gesloten vorm:

$$- {\color{red}{\int{\frac{\sin{\left(x \right)}}{x} d x}}} = - {\color{red}{\operatorname{Si}{\left(x \right)}}}$$

Dus,

$$\int{\left(- \frac{\sin{\left(x \right)}}{x}\right)d x} = - \operatorname{Si}{\left(x \right)}$$

Voeg de integratieconstante toe:

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

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