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

  • question_answer
    If in a \[\Delta ABC,\,\angle A={{45}^{o}},\,\,\angle C={{60}^{o}}\], then \[a+c\sqrt{2}=\] [MP PET 1999]

    A) b

    B) 2b

    C) \[\sqrt{2b}\]

    D) \[\sqrt{3}b\]

    Correct Answer: B

    Solution :

    \[A={{45}^{o}},C={{60}^{o}},A+B+C=\pi \Rightarrow B={{75}^{o}}\] Þ \[a+c\sqrt{2}=k\sin A+k\sin C(\sqrt{2})\]                  \[=k\sin {{45}^{o}}+\sqrt{2}k\sin {{60}^{o}}\]      \[=2k\left( \frac{\sqrt{3}+1}{2\sqrt{2}} \right)=2k\sin {{75}^{o}}=2k\sin B\] \ \[a+c\sqrt{2}=2b\].


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