(测试)LaTeX公式

\[a^2+b^2=c^2\]
\[F(\omega)=\mathcal{F}[f(t)]=\int_{-\infty}^\infty f(t)e^{-iwt}\,dt\]
\[\sum_{i=0}^n C_i^n =2^n\]
\[O(N\log N)\]
\[O (\sqrt{N^3})\]
\[\min_{1\le i \le N\\1\le j <i}\{\text{somthing}\}\]
\[f'(x)=\lim_{\Delta x \rightarrow 0} \frac{f(x+\Delta x)-f(x)}{\Delta x}\]