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JEE Main 2020
Logarithms
Logarithm
Easy

Question

The number of distinct solutions of the equation log12sinx=2log12cosx{\log _{{1 \over 2}}}\left| {\sin x} \right| = 2 - {\log _{{1 \over 2}}}\left| {\cos x} \right| in the interval [0, 2π\pi ], is ____.

Answer: 1

Solution

log12sinx=2log12cosx{\log _{{1 \over 2}}}\left| {\sin x} \right| = 2 - {\log _{{1 \over 2}}}\left| {\cos x} \right| \Rightarrow log12sinx{\log _{{1 \over 2}}}\left| {\sin x} \right| + log12cosx{\log _{{1 \over 2}}}\left| {\cos x} \right| = 2 \Rightarrow log12(sinxcosx){\log _{{1 \over 2}}}\left( {\left| {\sin x\cos x} \right|} \right) = 2 \Rightarrow sinxcosx=14{\left| {\sin x\cos x} \right| = {1 \over 4}} \Rightarrow sin 2x = ±\pm 12{1 \over 2} \therefore Number of distinct solution = 8

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