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10th Class Mathematics Introduction to Trigonometry Question Bank Trigonometry

  • question_answer
    The product \[\mathbf{cos}{{\mathbf{1}}^{{}^\circ }}\mathbf{cos}{{\mathbf{2}}^{{}^\circ }}\mathbf{cos}{{\mathbf{3}}^{{}^\circ }}\mathbf{cos}{{\mathbf{4}}^{{}^\circ }}.....\mathbf{cos18}{{\mathbf{0}}^{{}^\circ }}\]is equal to

    A)  -1                               

    B)  \[\frac{1}{4}\]

    C)  1                                

    D)  0

    Correct Answer: D

    Solution :

    (d): \[cos{{1}^{{}^\circ }}cos{{2}^{{}^\circ }}cos{{3}^{{}^\circ }}cos{{4}^{{}^\circ }}.....cos{{180}^{{}^\circ }}\]\[=0\left[ cos{{90}^{{}^\circ }}=0 \right]\]


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