JCECE Engineering JCECE Engineering Solved Paper-2006

  • question_answer
    \[{{\sin }^{2}}\theta =\frac{4xy}{{{(x+y)}^{2}}}\]is true, if and only if:

    A) \[x+y\ne 0\]                      

    B) \[x=y,\,\,x\ne 0,\,\,y\ne 0\]

    C) \[x=y\]                

    D) \[x\ne 0,\,\,y\ne 0\]

    Correct Answer: B

    Solution :

    Key Idea: \[{{\sin }^{2}}\theta \]is lies between \[0\] to\[1\]. We know that\[{{\sin }^{2}}\theta \ge 1\] \[\Rightarrow \]               \[\frac{4xy}{{{(x+y)}^{2}}}\ge 1\] \[\Rightarrow \]               \[4xy\ge {{(x+y)}^{2}}\] \[\Rightarrow \]               \[{{(x-y)}^{2}}\le 0\] \[\Rightarrow \]               \[x-y=0\] \[\Rightarrow \]               \[y=x\] and        \[x\ne 0,\,\,y\ne 0\]


You need to login to perform this action.
You will be redirected in 3 sec spinner