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JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Fundamental trigonometrical ratios and functions, Trigonometrical ratio of allied angles

  • question_answer
    \[\cos 1{}^\circ .\cos 2{}^\circ .\cos 3{}^\circ .........\cos 179{}^\circ =\] [Karnataka CET 1999; DCE 2005]

    A) 0

    B) 1

    C) 2

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

    Correct Answer: A

    Solution :

    We know that one of the factor of the given expression is \[\cos 90{}^\circ =0\]. Therefore\[\cos 1{}^\circ .\cos 2{}^\circ .\cos 3{}^\circ ...\cos 179{}^\circ =0\].


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