SSC Quantitative Aptitude Trigonometry Question Bank Trigonometry (I)

  • question_answer
    If \[\sin P+\text{cosec}\,P=2,\]then the value of \[{{\sin }^{7}}P+\cos e{{c}^{7}}P\] is   [SSC CGL Tier II, 2017]

    A) 1

    B) 2

    C) 3

    D) 0

    Correct Answer: B

    Solution :

    [b] \[\because \]\[\sin P\text{cosec}\,P=2\] \[\Rightarrow \]   \[\sin P+\frac{1}{\sin P}=2\]\[\Rightarrow \]\[{{\sin }^{2}}P+1=\sin P\] \[\Rightarrow \]   \[{{\sin }^{2}}P+1-2\sin P=0\] \[\Rightarrow \]   \[{{(\sin P-1)}^{2}}=0\] \[\Rightarrow \]   \[\sin P-1=0\] \[\Rightarrow \]   \[\sin P=1\] \[\therefore \]      \[{{\sin }^{7}}P+\text{cose}{{\text{c}}^{7}}P={{\sin }^{7}}P+\frac{1}{{{\sin }^{2}}P}\] \[={{(\sin P)}^{7}}+\frac{1}{{{(\sin P)}^{7}}}={{(1)}^{7}}+\frac{1}{{{(1)}^{7}}}=1+\frac{1}{1}=1+1=2\]


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