SSC Sample Paper Mock Test-16 SSC CGL Tear-II Paper-1

  • question_answer
    If \[\sin \theta +\cos \theta =m\]and \[\sec \theta +cosec\theta =n,\]then\[n\,\,({{m}^{2}}-1)\]is equal to

    A)  \[\frac{1}{2m}\]           

    B)  \[m\]

    C)  \[2\,\,m\]          

    D)  \[\frac{m}{2}\] 

    Correct Answer: C

    Solution :

    \[\sin \theta +\cos \theta =m\]
    and       \[\sec \theta +\text{cosec}\theta \text{=n}\]
    \[\Rightarrow \]   \[\frac{\sin \theta +\cos \theta }{\sin \theta \cos \theta }=n\]
    \[\Rightarrow \]   \[\frac{m}{\sin \theta \cos \theta }=n\]                 [from Eq. (i)]
    \[\Rightarrow \]   \[\frac{1}{\sin \theta \cos \theta }=\frac{n}{m}\]or\[\sin \theta \cos \theta =\frac{m}{n}\] Squaring Eq. (i)
    \[(si{{n}^{2}}\theta +co{{s}^{2}}\theta )+2sin\theta cos\theta ={{m}^{2}};1+2\frac{m}{n}={{m}^{2}}\]
    \[\Rightarrow \]   \[\frac{2\,\,m}{n}={{\text{m}}^{2}}-1\]\[\Rightarrow \]\[2m=({{\text{m}}^{2}}-1)n\]


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