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

  • question_answer
    The value of \[{{\sin }^{2}}30{}^\circ -{{\cos }^{2}}30{}^\circ \] is:                           (CBSE 2011)

    A) \[-\frac{1}{2}\]

    B) \[\frac{\sqrt{3}}{2}\]

    C) \[\frac{3}{2}\]

    D) \[\frac{2}{3}\]

    Correct Answer: A

    Solution :

    [a] \[{{\sin }^{2}}30{}^\circ -{{\cos }^{2}}30{}^\circ ={{\left( \frac{1}{2} \right)}^{2}}-{{\left( \frac{\sqrt{3}}{2} \right)}^{2}}\]
    \[=\frac{1}{4}-\frac{3}{4}=\frac{-2}{4}=\frac{-1}{2}\]


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