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

  • question_answer
    If the angles of a triangle be in the ratio 1 : 2 : 7, then the ratio of its greatest side to the least side is

    A) \[1:2\]

    B) 2 :1

    C) \[(\sqrt{5}+1):(\sqrt{5}-1)\]

    D) \[(\sqrt{5}-1):(\sqrt{5}+1)\]

    Correct Answer: C

    Solution :

    \[x+2x+7x={{180}^{o}}\Rightarrow x={{18}^{o}}\] Hence the angles are \[{{18}^{o}},\text{ }{{36}^{o}},\text{ }{{126}^{o}}\] Greatest side \[\propto \]\[\sin ({{126}^{o}})\] Smallest side \[\propto \] \[\sin ({{18}^{o}})\] and ratio\[=\frac{\sin {{126}^{o}}}{\sin ({{18}^{o}})}=\frac{\sqrt{5}+1}{\sqrt{5}-1}\].


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