JEE Main & Advanced Mathematics Trigonometric Equations Question Bank Solution of trigonometrical equations

  • question_answer
    If \[\tan (\pi \cos \theta )=\cot (\pi \sin \theta ),\]then the value of \[\cos \left( \theta -\frac{\pi }{4} \right)\]= [UPSEAT 1999]

    A) \[\frac{1}{2\sqrt{2}}\]

    B) \[\frac{1}{\sqrt{2}}\]

    C) \[\frac{1}{3\sqrt{2}}\]

    D) \[\frac{1}{4\sqrt{2}}\]

    Correct Answer: A

    Solution :

     \[\tan (\pi \cos \theta )=\tan \left( \frac{\pi }{2}-\pi \sin \theta  \right)\] \[\therefore \] \[\,\sin \theta +\cos \theta =\frac{1}{2}\]\[\Rightarrow \,\cos \left( \theta -\frac{\pi }{4} \right)=\frac{1}{2\sqrt{2}}\].


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