$$$e^{x^{2}} - \sin{\left(x \right)}$$$ 的积分

求$$$\int \left(e^{x^{2}} - \sin{\left(x \right)}\right)\, dx$$$。

逐项积分：

$${\color{red}{\int{\left(e^{x^{2}} - \sin{\left(x \right)}\right)d x}}} = {\color{red}{\left(\int{e^{x^{2}} d x} - \int{\sin{\left(x \right)} d x}\right)}}$$

正弦函数的积分为 $$$\int{\sin{\left(x \right)} d x} = - \cos{\left(x \right)}$$$:

$$\int{e^{x^{2}} d x} - {\color{red}{\int{\sin{\left(x \right)} d x}}} = \int{e^{x^{2}} d x} - {\color{red}{\left(- \cos{\left(x \right)}\right)}}$$

该积分（虚误差函数）没有闭式表达式：

$$\cos{\left(x \right)} + {\color{red}{\int{e^{x^{2}} d x}}} = \cos{\left(x \right)} + {\color{red}{\left(\frac{\sqrt{\pi} \operatorname{erfi}{\left(x \right)}}{2}\right)}}$$

因此，

$$\int{\left(e^{x^{2}} - \sin{\left(x \right)}\right)d x} = \cos{\left(x \right)} + \frac{\sqrt{\pi} \operatorname{erfi}{\left(x \right)}}{2}$$

加上积分常数：

$$\int{\left(e^{x^{2}} - \sin{\left(x \right)}\right)d x} = \cos{\left(x \right)} + \frac{\sqrt{\pi} \operatorname{erfi}{\left(x \right)}}{2}+C$$

$$$\int \left(e^{x^{2}} - \sin{\left(x \right)}\right)\, dx = \left(\cos{\left(x \right)} + \frac{\sqrt{\pi} \operatorname{erfi}{\left(x \right)}}{2}\right) + C$$$A