JEE Main & Advanced Sample Paper JEE Main Sample Paper-32

  • question_answer
           Angles A, B and C of a triangle ABC are in A.P. If  \[\frac{b}{c}=\sqrt{\frac{3}{2}}\]- then \[\angle A\] is equal to

    A) \[\pi /6\]     

    B)                    \[\pi /4\]

    C) \[5\pi /12\]   

    D)                    \[\pi /2\]

    Correct Answer: C

    Solution :

    \[2B=A+C\]and \[A+B+C=\pi \,\Rightarrow \,B=60{}^\circ \] Also \[\frac{\sin \,B}{\sin \,C}=\frac{\sqrt{3}}{\sqrt{2}}\,=\frac{\sqrt{3}}{2}.\frac{1}{\sin \,C}\] \[\sin \,C=\frac{1}{\sqrt{2}}\Rightarrow C=45{}^\circ \,\Rightarrow \,A=75{}^\circ \]


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