10th Class Mathematics Introduction to Trigonometry Question Bank Trigonometry

  • question_answer
    The value of \[\frac{\sin \theta }{1+\cos \theta }+\frac{\sin \theta }{1-{{\cos }^{2}}\theta }\] is\[\left( {{0}^{{}^\circ }}<\theta <{{90}^{{}^\circ }} \right)\]

    A) \[2\,cosec\theta \]

    B) \[2\,sec\theta \]

    C) \[2\,sin\theta \]

    D) \[2\,cos\theta \]

    Correct Answer: A

    Solution :

    (a): \[\frac{\sin \theta }{1+\cos \theta }+\frac{\sin \theta }{1-\cos \theta }\] \[\frac{sin\theta \left( 1-cos\theta  \right)+sin\theta \left( 1+cos\theta  \right)}{\left( 1+cos\theta  \right)\left( 1-cos\theta  \right)}\] \[=\frac{\sin \theta -\sin \theta cos\theta +sin\theta +\sin \theta .cos\theta }{1-co{{s}^{2}}\theta }\] \[=\frac{2sin\theta }{{{\sin }^{2}}\theta }=2\cos ec\theta \]


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