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

  • question_answer
    If \[\text{cosec A = }\sqrt{2},\]then the value of \[\frac{2{{\sin }^{2}}A+3{{\cot }^{2}}A}{4({{\tan }^{2}}A-{{\cos }^{2}}A)}\] is:

    A) 1

    B) 2

    C) 3

    D) 0

    Correct Answer: B

    Solution :

    [b] We have, \[\cos ec\,\,\,A=\sqrt{2}\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\angle A=45{}^\circ \] \[[\cos ec\,\,45{}^\circ =\sqrt{2}]\]
    \[\therefore \,\,\,\frac{2{{\sin }^{2}}A+3{{\cot }^{2}}A}{4({{\tan }^{2}}A-{{\cos }^{2}}A)}=\frac{2{{\sin }^{2}}45{}^\circ +3{{\cot }^{2}}45{}^\circ }{4({{\tan }^{2}}45{}^\circ -{{\cos }^{2}}45{}^\circ )}\]
    \[=\frac{2\times {{\left( \frac{1}{\sqrt{2}} \right)}^{2}}+3\times {{1}^{2}}}{4\left( {{1}^{2}}-{{\left( \frac{1}{\sqrt{2}} \right)}^{2}} \right)}=\frac{1+3}{4\times \frac{1}{2}}=\frac{4}{2}=2\]


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