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

  • question_answer
    The value of \[\frac{\tan \theta }{1+{{\tan }^{2}}\theta }\] is

    A) \[\frac{5}{12}\]

    B) \[\frac{5}{4}\]          

    C) \[\frac{60}{169}\]

    D) \[\frac{169}{60}\]

    Correct Answer: B

    Solution :

    \[\frac{\tan \theta }{1+{{\tan }^{2}}\theta }=\frac{\tan \theta }{{{\sec }^{2}}\theta }\]
    \[=\frac{\sin \theta }{\cos \theta }\times {{\cos }^{2}}\theta\]                   \[\left[ \because \,\tan \theta =\frac{\sin \theta }{\cos \theta } \right]\]
                                                    \[\left[ \because \,1+{{\tan }^{2}}\theta ={{\sec }^{2}}\theta  \right]\]
    \[=\sin \theta \times \cos \theta\]
    \[=\frac{PR}{PQ}\times \frac{RQ}{PQ}=\frac{9}{15}\times \frac{12}{15}\]
                                                    \[\left[ PR=\sqrt{225-144}=\sqrt{81}=9 \right]\]
    \[=\frac{12}{25}\]
     


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