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

  • question_answer
    If \[\cot \theta =\frac{1}{\sqrt{3}},\]then the value of \[\frac{1-{{\cos }^{2}}\theta }{2-{{\sin }^{2}}\theta }\] is:

    A) \[\frac{1}{5}\]

    B) \[\frac{2}{5}\]

    C) \[\frac{3}{5}\]

    D) \[\frac{5}{3}\]

    Correct Answer: C

    Solution :

    [c] We have, \[\cot \theta =\frac{1}{\sqrt{3}}\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\theta =60{}^\circ \]\[\left[ \cot 60{}^\circ =\frac{1}{\sqrt{3}} \right]\]
    \[\therefore \,\,\,\,\frac{1-{{\cos }^{2}}\theta }{2-{{\sin }^{2}}\theta }=\frac{1-{{\cos }^{2}}60{}^\circ }{2-{{\sin }^{2}}60{}^\circ }\]
    \[=\frac{1-{{\left( \frac{1}{2} \right)}^{2}}}{2-{{\left( \frac{\sqrt{3}}{2} \right)}^{2}}}=\frac{1-\frac{1}{4}}{2-\frac{3}{4}}=\frac{\frac{4-1}{4}}{\frac{8-3}{4}}=\frac{3}{5}\]


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