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

  • question_answer
    If\[\sec \theta =x+\frac{1}{4x}\], then the value of \[\sec \theta +\tan \theta \] is

    A) 4x

    B) 2x

    C) x

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

    Correct Answer: B

    Solution :

    Given, \[\sec \theta =x+\frac{1}{4x}\]
    Squaring both sides, we get
    \[{{\sec }^{2}}\theta ={{\left( x+\frac{1}{4x} \right)}^{2}}\]
    \[={{x}^{2}}+\frac{1}{16{{x}^{2}}}+\frac{1}{2}\]
    \[{{\sec }^{2}}\theta -1={{x}^{2}}+\frac{1}{16{{x}^{2}}}-\frac{1}{2}\]
    \[{{\sec }^{2}}\theta -1={{\left( x-\frac{1}{4x} \right)}^{2}}\]
    \[{{\tan }^{2}}\theta ={{\left( x-\frac{1}{4x} \right)}^{2}}\]
    \[\left[ \because \,{{\sec }^{2}}\theta -1\,={{\tan }^{2}}\theta  \right]\]
    \[\tan \,\theta =\underline{+}\left( x-\frac{1}{4x} \right)\]
    \[\sec \theta +\tan \theta \]
    \[x+\frac{1}{4x}+x-\frac{1}{4x}=2x\]


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