J & K CET Engineering J and K - CET Engineering Solved Paper-2003

  • question_answer
    In a triangle ABC, \[2ca\,\sin \left( \frac{A-B+C}{2} \right)\] is equal to

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

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

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

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

    Correct Answer: B

    Solution :

    Now \[2\,ca\,\sin \,\left( \frac{A-B+C}{2} \right)\] \[=2\,ca\,\sin \,\left( \frac{\pi }{2}-\frac{B}{2}-\frac{B}{2} \right)\] \[(\because \,\,A+B+C=\pi )\] \[=2\,ca\,\cos B=2ca.\frac{{{a}^{2}}+{{c}^{2}}-{{b}^{2}}}{2ac}={{a}^{2}}+{{c}^{2}}-{{b}^{2}}\]


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