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

  • question_answer
    In a \[\Delta ABC,\] \[A:B:C\]. Then \[[a+b+c\sqrt{2}]\] is equal to [DCE 2001]

    A) 2b

    B) 2c

    C) 3b

    D) 3a

    Correct Answer: C

    Solution :

    \[\because \] \[A:B:C=3:5:4\] Þ  \[A+B+C=12x={{180}^{o}}\,\,\Rightarrow \,\,x={{15}^{o}}\] \[\therefore \] \[A={{45}^{o}},\,B={{75}^{o}},\,C={{60}^{o}}\] \[\frac{a}{\sin {{45}^{o}}}=\frac{b}{\sin {{75}^{o}}}=\frac{c}{\sin {{60}^{o}}}=K\]    (say) \[\therefore \,a=\frac{1}{\sqrt{2}}K,\,\,\,\,b=\frac{\sqrt{3}+1}{2\sqrt{2}}K,\,\,\,\,c=\frac{\sqrt{3}}{2}K\] \[\therefore \,\,a+b+c\sqrt{2}=3b.\]


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