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NCERT Class XI Mathematics - Trigonometric Functions - Solutions

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Question : 45 of 61
Marks: +1, -0
cot x = − 3\sqrt{3}
Solution:  
cot x = − 3\sqrt{3} ⇒ tan x = 13-\frac{1}{\sqrt{3}}
A value of x satisfying tanx = 13\frac{1}{\sqrt{3}} is π6\frac{\pi}{6}
Principal Solution : We have tanx = 13-\frac{1}{\sqrt{3}}
Thus , tan (ππ6)\left(\pi - \frac{\pi}{6}\right) = - tan π6\frac{\pi}{6} = 13\frac{-1}{\sqrt{3}} and , tan (2ππ6)\left(2\pi - \frac{\pi}{6}\right) = - tan π6\frac{\pi}{6} = - 13\frac{1}{\sqrt{3}}
Thus , tan 5π6\frac{5\pi}{6} = tan 11π6\frac{11\pi}{6} = 13\frac{-1}{\sqrt{3}}
Therefore principal solutions are 5π6,11π6\frac{5\pi}{6},\frac{11\pi}{6}
General Solution :
We have, tanx = 13\frac{-1}{\sqrt{3}}
⇒ tan x = tan (ππ6)\left(\pi - \frac{\pi}{6}\right) = tan 5π6\frac{5\pi}{6} ⇒ x = nπ + 5π6\frac{5\pi}{6} , n ∊ Z
Since tan x = tan α , then x = nπ + α , n ∊ Z
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