Question
Evaluate the following limit: $\lim\limits_{\text{x}\rightarrow\frac{\pi}{3}}\frac{\sqrt{1-\cos6\text{x}}}{\sqrt{2}\big(\frac{\pi}{3}-\text{x}\big)}$

Answer

$\lim\limits_{\text{x}\rightarrow\frac{\pi}{3}}\frac{\sqrt{1-\cos6\text{x}}}{\sqrt{2}\big(\frac{\pi}{3}-\text{x}\big)}$ $=\lim\limits_{\text{x}\rightarrow\frac{\pi}{3}}\frac{\sqrt{2\sin^23\text{x}}}{\sqrt{2}\big(\frac{\pi}{3}-\text{x}\big)}$ $\big(1-\cos2\theta=2\sin^2\theta\big)$ $=\lim\limits_{\text{x}\rightarrow\frac{\pi}{3}}\frac{\sqrt{2}\sin3\text{x}}{\sqrt{2}\big(\frac{\pi}{3}-\text{x}\big)}$ $=\lim\limits_{\text{x}\rightarrow\frac{\pi}{3}}\frac{\sin3\text{x}}{\big(\frac{\pi}{3}-\text{x}\big)}$ $=\lim\limits_{\text{h}\rightarrow0}\frac{\sin3\big(\frac{\pi}{3}+\text{h}\big)}{\frac{\pi}{3}-\big(\frac{\pi}{3}-\text{x}\big)}$ $\big(\text{Put x}=\frac{\pi}{3}+\text{h}\big)$ $=\lim\limits_{\text{h}\rightarrow0}\frac{\sin(\pi+3\text{h})}{-\text{h}}$ $=\lim\limits_{\text{h}\rightarrow0}\frac{-\sin3\text{h}}{-\text{h}}$ $[\sin(\pi+\theta)=-\sin\theta]$ $=3\times\lim\limits_{\text{h}\rightarrow0}\frac{\sin3\text{h}}{3\text{h}}$ $3\times1$ $\Big(\lim\limits_{\theta\rightarrow0}\frac{\sin\theta}{\theta}=1\Big)$ $=3$

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