3.Trigonometrical Ratios, Functions and Identities
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दी गई आकृति में $\theta_1+\theta_2=\frac{\pi}{2}$ तथा

$\sqrt{3}(\mathrm{BE})=4(\mathrm{AB})$ है। यदि $\triangle \mathrm{CAB}$ का क्षेत्रफल

$2 \sqrt{3}-3$ वर्ग इकाई है, जब $\frac{\theta_2}{\theta_1}$ अधिकतम है, तो

$\triangle \mathrm{CED}$ का परिमाप (इकाई में) बराबर है :

A

$5$

B

$4$

C

$6$

D

$3$

(JEE MAIN-2023)

Solution

$\sqrt{3} BE =4 AB$

$Ar (\triangle CAB )=2 \sqrt{3}-3$

$\frac{1}{2} x ^2 \tan \theta_1=2 \sqrt{3}-3$

$BE = BD + DE$

$= x \left(\tan \theta_1+\tan \theta_2\right)$

$BE = AB \left(\tan \theta_1+\cot \theta_1\right)$

$\frac{4}{\sqrt{3}} \tan \theta_1+\cot \theta_1 \Rightarrow \tan \theta_1=\sqrt{3}, \frac{1}{\sqrt{3}}$

$\theta_1=\frac{\pi}{6}$

$\theta_1=\frac{\pi}{3} \quad \theta_2=\frac{\pi}{3}$

$as \frac{\theta_2}{\theta_1} \text { is } \operatorname{largest} \therefore \theta_1=\frac{\pi}{6} \theta_2=\frac{\pi}{3}$

$\therefore x ^2=\frac{(2 \sqrt{3}-3) \times 2}{\tan \theta_1}=\frac{\sqrt{3}(2-\sqrt{3}) \times 2}{\tan \frac{\pi}{6}}$

$x ^2=12-6 \sqrt{3}=(3-\sqrt{3})^2$

$x =3-\sqrt{3}$

Perimeter of $\triangle C E D$

$= CD + DE + CE$

$=3 \sqrt{3}+(3-\sqrt{3}) \sqrt{3}+(3-\sqrt{3}) \times 2=6$

Standard 11
Mathematics

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