测试文档

$$
\begin{align}
\int_0^Y T_M(y) \mathrm{d}y &= \int_0^Y \left( T_{M0} - \frac{\Omega^2 T_0}{2 a^2 g H} y^4 \right) \mathrm{d}y \
&= T_{M0} y - \frac{\Omega^2 T_0}{2 a^2 g H} \frac{y^5}{5} \Bigg|0^Y \
&= T{M0} Y - \frac{\Omega^2 T_0}{10 a^2 g H} Y^5
\end{align}\tag{2.21}
$$