Question
Evaluate the following limit: $\lim\limits_{\text{x}\rightarrow0}\frac{\text{cosec x}-\cot\text{x}}{\text{x}}$

Answer

$\lim\limits_{\text{x}\rightarrow0}\frac{\text{cosec x}-\cot\text{x}}{\text{x}}$ $=\lim\limits_{\text{x}\rightarrow0}\Big(\frac{1}{\sin\text{x}}-\frac{\cos\text{x}}{\sin\text{x}}\Big)\times\frac{1}{\text{x}}$ $=\lim\limits_{\text{x}\rightarrow0}\Big(\frac{1}{\sin\text{x}}\Big(\frac{1-\cos\text{x}}{\text{x}}\Big)\Big)$ $=\lim\limits_{\text{x}\rightarrow0}\bigg(\frac{1}{\sin\text{x}}\bigg(\frac{2\sin^2\frac{\text{x}}{2}}{\text{x}}\bigg)\bigg)$ $=2\lim\limits_{\text{x}\rightarrow0}\Bigg(\frac{1}{\frac{\sin\text{x}}{\text{x}}}\times\text{x}\bigg(\frac{\sin\frac{\text{x}}{2}}{\frac{\text{x}}{2}}\bigg)\times\frac{\text{x}}{4}\Bigg)$ $=2\bigg(\lim\limits_{\text{x}\rightarrow0}\frac{1}{\frac{\sin\text{x}}{\text{x}}}\bigg)\times\frac{1}{\text{x}}\times\bigg(\lim\limits_{\text{x}\rightarrow0}\frac{\sin\frac{\text{x}}{2}}{\frac{\text{x}}{2}}\bigg)\times\frac{\text{x}}{4}$ $=2\times\frac{1}{\text{x}}\times\frac{\text{x}}{4}$ $=\frac{1}{2}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free