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

  • question_answer
    If \[\sin A=\frac{1}{2},\]then the value of \[\cot A\] is:                                                        (NCERT EXEMPLAR)

    A) \[\sqrt{3}\]

    B) \[\frac{1}{\sqrt{3}}\]

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

    D) \[1\]

    Correct Answer: A

    Solution :

    [a] Given, \[\sin A=\frac{1}{2}\]
    \[\cos A=\sqrt{1-{{\sin }^{2}}A}\]\[[{{\sin }^{2}}A+{{\cos }^{2}}A=1]\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\cos A=\sqrt{1-{{\left( \frac{1}{2} \right)}^{2}}}=\sqrt{1-\frac{1}{4}}=\sqrt{\frac{3}{4}}=\frac{\sqrt{3}}{2}\]
    Now,\[\cot A=\frac{\cos A}{\sin A}=\frac{\sqrt{3}/2}{1/2}=\sqrt{3}\]
    Hence, the required value of cot A is \[\sqrt{3}\]. 


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