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JEE Main & Advanced Mathematics Trigonometric Equations Question Bank Relation between sides and angles, Solutions of triangles

  • question_answer
    In \[\Delta ABC\], if \[a=3,b=4,c=5\], then \[\sin 2B=\]  [MP PET 1983]

    A) 4/5

    B) 3/20

    C) 24/25

    D) 1/50

    Correct Answer: C

    Solution :

    \[\cos B=\frac{9+25-16}{2.3.5}=\frac{18}{2.3.5}=\frac{3}{5}\Rightarrow \sin B=\frac{4}{5}\] Therefore\[\sin 2B=2.\frac{4}{5}.\frac{3}{5}=\frac{24}{25}\].


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