SSC Quantitative Aptitude Trigonometry Question Bank Trigonometry (I)

  • question_answer
    If \[x=\sin \theta +\cos \theta \]and\[y=\text{sec}\theta +\text{cosec}\theta ,\]find y in terms of x

    A) \[\frac{x}{{{x}^{2}}+1}\]

    B) \[\frac{x}{{{x}^{2}}-1}\]

    C) \[\frac{2x}{{{x}^{2}}-1}\]

    D) \[\frac{2x}{{{x}^{2}}+1}\]

    Correct Answer: C

    Solution :

    [c] \[x=\sin \theta +\cos \theta \]                          ...(i) \[y=\sec \theta +\text{cosec}\theta \] \[=\frac{1}{\sin \theta }+\frac{1}{\cos \theta }\] \[=\frac{\sin \theta +\cos \theta }{\sin \theta \cos \theta }\] \[=\frac{x}{\sin \theta cos\theta }\] \[\because \]\[{{(sin\theta +cos\theta )}^{2}}=1+2\sin \theta \cos \theta \] \[{{x}^{2}}=1+2\sin \theta cos\theta \] \[\sin \theta \cos \theta =\frac{{{x}^{2}}-1}{2}\]            [from Eq. (ii)]                         \[y=\frac{2x}{{{x}^{2}}-1}\]


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