Manipal Engineering Manipal Engineering Solved Paper-2010

  • question_answer
    The locus of the point of intersection of tangents to the circle\[x=a\cos \theta ,\,\,y=a\sin \theta \]at the points, whose parametric angles differe by\[\frac{\pi }{2}\], is

    A)  a straight line

    B)  a circle

    C)  a pair of straight line

    D)  None of the above

    Correct Answer: B

    Solution :

    We have, the given circle\[x=a\cos \theta ,\,\,y=a\sin \theta \]                 \[{{x}^{2}}+{{y}^{2}}={{a}^{2}}\]                                               ... (i) Tangents to the circle (i) at\[\theta \]and\[\left( \theta +\frac{\pi }{2} \right)\]are                 \[x\cos \theta +y\sin \theta =a\] and        \[x\cos \left( \theta +\frac{\pi }{2} \right)+y\sin \left( \theta +\frac{\pi }{2} \right)=a\] or            \[x\cos \theta +y\sin \theta =a\] and        \[-x\sin \theta +y\cos \theta =a\] Squaring and adding, we get\[{{x}^{2}}+{{y}^{2}}=2{{a}^{2}}\] which is a circle.


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