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

  • question_answer
    \[\frac{\sin \theta -2{{\sin }^{2}}\theta }{2{{\cos }^{3}}\theta -\cos \theta }\] is equal to _______.

    A) \[\frac{{{\sin }^{2}}\theta }{\cos \theta }\] 

    B)        \[\tan \theta \]  

    C)  \[\frac{{{\cos }^{2}}\theta }{\sin \theta }\]

    D)         \[\cot \theta \] 

    Correct Answer: B

    Solution :

    \[\frac{\sin \theta -2{{\sin }^{3}}\theta }{2{{\cos }^{3}}\theta -\cos \theta }=\frac{\sin \theta }{\cos \theta }\,\left[ \frac{1-2{{\sin }^{2}}\theta }{2{{\cos }^{2}}\theta -1} \right]\] \[=\frac{\sin \theta }{\cos \theta }\left[ \frac{1-2(1-{{\cos }^{2}}\theta )}{2{{\cos }^{2}}\theta -1} \right]\] \[=\frac{\sin \theta }{\cos \theta }\left[ \frac{2{{\cos }^{2}}\theta -1}{2{{\cos }^{2}}\theta -1} \right]=\tan \theta \]


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