CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2008

  • question_answer
    If a line makes angles\[\alpha ,\beta ,\gamma \]and \[\delta \] with four diagonals of a cube, then the value of \[si{{n}^{2}}\alpha +si{{n}^{2}}\beta +si{{n}^{2}}\gamma +si{{n}^{2}}\delta \]is

    A)  \[\frac{4}{3}\]                  

    B)         \[\frac{8}{3}\]

    C)  \[\frac{7}{3}\]                  

    D)         \[1\]

    E)  None of these

    Correct Answer: B

    Solution :

    We know that, \[{{\cos }^{2}}\alpha +{{\cos }^{2}}\beta +{{\cos }^{2}}\gamma +{{\cos }^{2}}\delta =\frac{4}{3}\]        ...(i) where\[\alpha ,\beta ,\gamma \]and\[\delta \]are the angles with diagonals of cube, then from Eq. (i), we get \[1-{{\sin }^{2}}\alpha +1-{{\sin }^{2}}\beta +1-{{\sin }^{2}}\gamma +1-{{\sin }^{2}}\delta =\frac{4}{3}\] \[\Rightarrow \]\[{{\sin }^{2}}\alpha +si{{n}^{2}}\beta +{{\sin }^{2}}\gamma +{{\sin }^{2}}\delta =\frac{8}{3}\]


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