JCECE Engineering JCECE Engineering Solved Paper-2009

  • question_answer
    Find the equation of tangents to the ellipse\[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\], which cut off equal intercepts or the axes.

    A) \[y=\sqrt{3}x\pm \sqrt{3{{a}^{2}}+{{b}^{2}}}\]

    B) \[y=\pm x\mp \sqrt{{{a}^{2}}+{{b}^{2}}}\]

    C) \[y=\sqrt{3}\pm \sqrt{{{a}^{2}}+3{{b}^{2}}}\]

    D)  None of the above

    Correct Answer: B

    Solution :

    Let the equation of line of equal intercept is                 \[y\pm x=\pm c\]                 \[y=\pm x\mp c\] Since, this line is tangent to the ellipse                 \[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\] \[\therefore \]  \[c=\sqrt{{{a}^{2}}+{{b}^{2}}}\] \[\therefore \]Required line is                 \[y=\pm x\mp \sqrt{{{a}^{2}}+{{b}^{2}}}\] Hence, option  is correct.


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