RAJASTHAN ­ PET Rajasthan PET Solved Paper-2006

  • question_answer
    In a\[\Delta ABC,{{r}_{1}},{{r}_{2}},{{r}_{3}}\]are in harmonic series, then a, b, c are in

    A)  AP             

    B)  GP

    C)  HP             

    D)  None of these

    Correct Answer: A

    Solution :

     If\[{{r}_{1}},{{r}_{2}},{{r}_{3}}\]are in HP. \[\Rightarrow \] \[\frac{1}{{{r}_{1}}},\frac{1}{{{r}_{2}}},\frac{1}{{{r}_{3}}}\]are in AP. \[\Rightarrow \] \[\frac{s-a}{\Delta },\frac{s-b}{\Delta },\frac{s-c}{\Delta }\]are in AP. \[\left[ \because {{r}_{1}}=\frac{\Delta }{s-a},{{r}_{2}}=\frac{\Delta }{s-b},{{r}_{3}}=\frac{\Delta }{s-c} \right]\] \[\Rightarrow \] \[(s-a),(s-b),\text{(}s-c)\]are in AP. \[\Rightarrow \]a, b, c are in AP.


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