JEE MATHEMATICS MCQ: TRIGONOMETRIC EQUATIONS

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Application +4 | -1

If in a triangle

\cos 3 \mathrm{~A}+\cos 3 \mathrm{~B}+\cos 3 \mathrm{C}=1

then one angle must be exactly equal to -

View answer and explanation

Correct option: D

120^{\circ}

Option D (

120^{\circ}

) is correct. By using trigonometric identities and the given equation, we can deduce that one of the angles must be

\frac{{2\pi}}{{3}}

, which is

120^{\circ}

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\mathrm{X}

\theta \rightarrow \frac{\pi}{2}

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