BCECE Engineering BCECE Engineering Solved Paper-2012

  • question_answer
    In \[\Delta ABC,2ac\,\sin \frac{A-B+C}{2}\]is equal to

    A)  \[{{a}^{2}}+{{b}^{2}}-{{c}^{2}}\]                              

    B)         \[{{c}^{2}}+{{a}^{2}}-{{b}^{2}}\]                              

    C)         \[{{b}^{2}}-{{a}^{2}}-{{c}^{2}}\]               

    D)         \[{{c}^{2}}-{{a}^{2}}-{{b}^{2}}\]

    Correct Answer: B

    Solution :

    \[2ac\,\sin \left( \frac{A-B+C}{2} \right)\] \[=2ac\,\sin \left( \frac{180-2B}{2} \right)\]                 \[=2ac\sin ({{90}^{o}}-B)=2ac\,\cos \,B\] \[={{a}^{2}}+{{c}^{2}}-{{b}^{2}}\]


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