10th Class Mathematics Introduction to Trigonometry Question Bank MCQs - Introduction to Trigonometry

  • question_answer
    If \[4x=\cos ec\theta \]and \[\frac{4}{x}=\cot \theta \], then the value of \[4\left[ {{x}^{2}}-\frac{1}{{{x}^{2}}} \right]\]is

    A) \[\frac{1}{4}\]

    B) 4

    C) 2

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

    Correct Answer: A

    Solution :

    Given, \[4x=\cos ec\theta \] and \[\frac{4}{x}=\cot \,\theta \] \[x=\frac{\cos ec\theta }{4}\] and \[\frac{1}{x}=\frac{\cot \theta }{4}\] We have find the value of \[4\left[ {{x}^{2}}-\frac{1}{{{x}^{2}}} \right]\] \[=4\left[ {{\left( \frac{\cos ec\theta }{4} \right)}^{2}}-{{\left( \frac{\cot \theta }{4} \right)}^{2}} \right]\] \[=4\left[ \frac{\cos e{{c}^{2}}\theta }{16}-\frac{{{\cot }^{2}}\theta }{16} \right]\] \[=\frac{4}{16}\left[ \cos e{{c}^{2}}\theta -{{\cot }^{2}}\theta  \right]=\frac{1}{4}\]


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