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

  • question_answer
    If \[7{{\sin }^{2}}A+3{{\cos }^{2}}A=4,\] then \[\tan A\] is equal to:

    A) \[\sqrt{3}\]

    B) \[1\]

    C) \[0\]

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

    Correct Answer: D

    Solution :

    [d]\[7{{\sin }^{2}}A+3{{\cos }^{2}}A=4\]
    \[\Rightarrow \,\,\,4{{\sin }^{2}}A+3({{\sin }^{2}}A+{{\cos }^{2}}A)=4\]
    \[\Rightarrow \,\,\,\,\,4{{\sin }^{2}}A+3\times 1=4\]\[[{{\sin }^{2}}\theta +{{\cos }^{2}}\theta =1]\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,4{{\sin }^{2}}A=1\,\,\,\,\,\,\,\,\Rightarrow \,\,\,\,\,\sin A=\frac{1}{2}=\sin 30{}^\circ \]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,A=30{}^\circ \]
    \[\therefore \,\,\,\,\,\,\,\,\,\,\,\tan A=\tan 30{}^\circ =\frac{1}{\sqrt{3}}\]


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