一、题目![题目 - 荒原之梦](https://documents.zhaokaifeng.com/uploads/2017/06/06/f68a9e590526998388b0f9b71bd5d3f73dda4ed9764819fe8f36488fa537e9b9499f465fd201d7c117b8901c3ad071915a34a688058a739ebc39835753a8d7cc.svg)
$$
\cos (\arcsin y) = ?
$$
已知 $a$ 为常数,计算如下定积分:
$$
\int \frac{1}{a^{2} + x^{2}} \mathrm{d} x
$$
$\textcolor{cyan}{\lambda}$ $\textcolor{orange}{(}$ $\boldsymbol{A B}$ $\textcolor{orange}{)}$ $=$ $\textcolor{orange}{(}$ $\textcolor{cyan}{\lambda}$ $\boldsymbol{A}$ $\textcolor{orange}{)}$ $\boldsymbol{B}$ $=$ $\boldsymbol{A}$ $\textcolor{orange}{(}$ $\textcolor{cyan}{\lambda}$ $\boldsymbol{B}$ $\textcolor{orange}{)}$