CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2005

  • question_answer
    The angle between the pair of straight lines\[{{y}^{2}}{{\sin }^{2}}\theta -xy{{\sin }^{2}}\theta +{{x}^{2}}({{\cos }^{2}}\theta -1)=0\]is:

    A)  \[\frac{\pi }{3}\]                             

    B)         \[\frac{\pi }{4}\]

    C)  \[\frac{\pi }{6}\]                             

    D)         \[\frac{\pi }{2}\]

    E)  \[\pi \]

    Correct Answer: D

    Solution :

    The given equation is \[{{x}^{2}}({{\cos }^{2}}\theta -1)-xy{{\sin }^{2}}\theta +{{y}^{2}}{{\sin }^{2}}\theta =0\] On comparing with \[a{{x}^{2}}+2hxy+b{{y}^{2}}=0,\]we get \[a={{\cos }^{2}}\theta -1,h=-\frac{1}{2}{{\sin }^{2}}\theta ,b={{\sin }^{2}}\theta \] \[\because \]\[a+b={{\cos }^{2}}\theta +{{\sin }^{2}}\theta -1=1-1=0\] \[\therefore \]The angle between the pair of straight lines is\[\frac{\pi }{2}\].


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