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

  • question_answer
    \[\cos 1{}^\circ +\cos 2{}^\circ +\cos 3{}^\circ +.....+\cos 180{}^\circ =\] [Karnataka CET 2003]

    A) 0

    B) 1

    C) -1

    D) 2

    Correct Answer: C

    Solution :

    \[(\cos 1{}^\circ +\cos 179{}^\circ )+(\cos 2{}^\circ +\cos 178{}^\circ )+....\] \[+(\cos 89{}^\circ +\cos 91{}^\circ )+\cos 90{}^\circ +\cos 180{}^\circ =-1\].


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