JEE Main & Advanced Mathematics Trigonometric Equations Question Bank Circle connected with triangle

  • question_answer
    If \[x,\,y,\,z\]are perpendicular drawn \[a,\,b\] and \[c\], then the value of  \[\frac{bx}{c}+\frac{cy}{a}+\frac{az}{b}\]will be [UPSEAT 1999]

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

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

    C) \[\frac{{{a}^{2}}+{{b}^{2}}+{{c}^{2}}}{4R}\]

    D) \[\frac{2({{a}^{2}}+{{b}^{2}}+{{c}^{2}})}{R}\]

    Correct Answer: A

    Solution :

    Let area of triangle be\[\Delta \], then according to question, \[\Delta =\frac{1}{2}ax=\frac{1}{2}by=\frac{1}{2}cz\] \[\therefore \] \[\,\frac{bx}{c}+\frac{cy}{a}+\frac{az}{b}=\frac{b}{c}\left( \frac{2\Delta }{a} \right)+\frac{c}{a}\left( \frac{2\Delta }{b} \right)+\frac{a}{b}\left( \frac{2\Delta }{c} \right)\]      \[=\frac{2\Delta ({{b}^{2}}+{{c}^{2}}+{{a}^{2}})}{abc}=\frac{2({{a}^{2}}+{{b}^{2}}+{{c}^{2}})}{abc}\text{ }\text{. }\frac{abc}{4R}=\frac{{{a}^{2}}+{{b}^{2}}+{{c}^{2}}}{2R}\].


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