Question
Evaluate the following limit: $\lim\limits_{\text{x}\rightarrow0}\frac{\text{x}\tan\text{x}}{1-\cos2\text{x}}$

Answer

$\lim\limits_{\text{x}\rightarrow0}\frac{\text{x}\tan\text{x}}{1-\cos2\text{x}}$ $=\lim\limits_{\text{x} \rightarrow0}\frac{\text{x}\tan\text{x}}{2\sin^2\text{x}}$ $=\lim\limits_{\text{x} \rightarrow0}\frac{\frac{\tan\text{x}}{\text{x}}}{\frac{2\sin^2\text{x}}{\text{x}^2}}$ $=\frac{\lim\limits_{\text{x} \rightarrow0}\frac{\tan\text{x}}{\text{x}}}{2\lim\limits_{\text{x} \rightarrow0}\big(\frac{\sin\text{x}}{\text{x}}\big)^2}$ $\Big[\because\lim\limits_{\theta\rightarrow0}\frac{\sin\theta}{\theta}=1,\lim\limits_{\theta\rightarrow0}\frac{\tan\theta}{\theta}=1\Big]$ $=\frac{1}{2\times1}$ $=\frac{1}{2}$

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