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

  • question_answer
    If\[\tan \theta =\frac{1}{\tan \theta }=2\], then the value of \[\cos ec\,\theta \] is

    A) 1

    B) \[\frac{1}{\sqrt{2}}\]

    C) \[\sqrt{2}\]

    D) \[\frac{\sqrt{3}}{2}\]

    Correct Answer: C

    Solution :

    Given, \[\tan \theta +\frac{1}{\tan \theta }=2\] \[\Rightarrow \,\,{{\tan }^{2}}\theta +1=2\tan \theta \] \[\Rightarrow \,\,{{\tan }^{2}}\theta -2\tan \theta +1=0\] \[\Rightarrow \,\,{{\left( \tan \theta -1 \right)}^{2}}=0\] \[\Rightarrow \,\tan \theta =1\] \[\Rightarrow \,\,\tan \theta =\tan 45{}^\circ \] \[\Rightarrow \,\,\theta =45{}^\circ \] \[\Rightarrow \,\,\cos ec\,45{}^\circ =\sqrt{2}\]


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