10th Class Mathematics Introduction to Trigonometry Question Bank Trigonometry

  • question_answer
    \[\frac{\sin \theta +\cos \theta }{\sin \theta -\cos \theta }+\frac{\sin \theta -\cos \theta }{\sin \theta +\cos \theta }=\]

    A)  \[\frac{2}{1-2\,{{\cos }^{2}}\theta }\]              

    B)  \[\frac{2}{2\,{{\sin }^{2}}\theta -1}\]

    C)  both (a) & (b)   

    D)  None of these

    Correct Answer: C

    Solution :

    (c): \[\frac{{{(sin\theta +cos\theta )}^{2}}+{{(sin\theta -cos\theta )}^{2}}}{{{\sin }^{2}}\theta -{{\cos }^{2}}\theta }\] \[=\frac{{{\sin }^{2}}\theta +{{\cos }^{2}}\theta +2\sin \theta \cos \theta +{{\sin }^{2}}\theta +{{\cos }^{2}}\theta -2\sin \theta \cos \theta }{{{\sin }^{2}}\theta -{{\cos }^{2}}\theta }\] \[=\frac{2}{{{\sin }^{2}}\theta -{{\cos }^{2}}\theta }=\frac{2}{1-2{{\cos }^{2}}\theta }=\frac{2}{2{{\sin }^{2}}\theta -1}\]


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