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$$$2 \cos{\left(x^{2} \right)}$$$の積分
入力内容
$$$\int 2 \cos{\left(x^{2} \right)}\, dx$$$ を求めよ。
解答
定数倍の法則 $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$ を、$$$c=2$$$ と $$$f{\left(x \right)} = \cos{\left(x^{2} \right)}$$$ に対して適用する:
$${\color{red}{\int{2 \cos{\left(x^{2} \right)} d x}}} = {\color{red}{\left(2 \int{\cos{\left(x^{2} \right)} d x}\right)}}$$
この積分（フレネル余弦積分）には閉形式はありません:
$$2 {\color{red}{\int{\cos{\left(x^{2} \right)} d x}}} = 2 {\color{red}{\left(\frac{\sqrt{2} \sqrt{\pi} C\left(\frac{\sqrt{2} x}{\sqrt{\pi}}\right)}{2}\right)}}$$
したがって、
$$\int{2 \cos{\left(x^{2} \right)} d x} = \sqrt{2} \sqrt{\pi} C\left(\frac{\sqrt{2} x}{\sqrt{\pi}}\right)$$
積分定数を加える:
$$\int{2 \cos{\left(x^{2} \right)} d x} = \sqrt{2} \sqrt{\pi} C\left(\frac{\sqrt{2} x}{\sqrt{\pi}}\right)+C$$
解答
$$$\int 2 \cos{\left(x^{2} \right)}\, dx = \sqrt{2} \sqrt{\pi} C\left(\frac{\sqrt{2} x}{\sqrt{\pi}}\right) + C$$$A