Trigonometric Function
\[\lim _{\theta \rightarrow 0} \frac {\sin \theta}{\theta}=1\]
\[A_{\triangle OAB}<A_{Sector OAB}<A_{\triangle OAC}\]
\[ \frac{1}{2}\sin\theta<\frac{1}{2}\theta<\frac{1}{2}\tan\theta\]
\[\lim _{\theta \rightarrow 0} \frac {\sin \theta}{\theta}=1\]
\[A_{\triangle OAB}<A_{Sector OAB}<A_{\triangle OAC}\]
\[ \frac{1}{2}\sin\theta<\frac{1}{2}\theta<\frac{1}{2}\tan\theta\]