SSC Quantitative Aptitude Trigonometry Question Bank Trigonometry (I)

  • question_answer
    If \[\sin \theta +{{\sin }^{2}}\theta -1,\]then the value of \[{{\cos }^{12}}\theta +3{{\cos }^{10}}\theta +3{{\cos }^{8}}\theta +{{\cos }^{6}}\theta -1\]is

    A) \[0\]

    B) \[1\]

    C) \[-1~\]

    D) \[2\]

    Correct Answer: A

    Solution :

    [a] Given, \[\sin \theta +{{\sin }^{2}}\theta =1\] \[\Rightarrow \]   \[\sin \theta =1-{{\sin }^{2}}\theta \] \[\Rightarrow \]   \[\sin \theta ={{\cos }^{2}}\theta \]…(i) \[{{\cos }^{12}}\theta +3{{\cos }^{10}}\theta +3\,co{{s}^{8}}\theta +{{\cos }^{6}}\theta -1\] \[={{(co{{s}^{4}}\theta +co{{s}^{2}}\theta )}^{3}}-1\] \[={{(si{{n}^{2}}\theta +co{{s}^{2}}\theta )}^{2}}-1\] \[={{(1)}^{2}}-1=0\]


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