JCECE Engineering JCECE Engineering Solved Paper-2004

  • question_answer
    If\[\sin x+\cos x=\frac{1}{5}\], then\[\tan 2x\]is:

    A) \[\frac{25}{17}\]                                              

    B) \[\frac{24}{7}\]

    C) \[\frac{7}{25}\]                                

    D) \[\frac{25}{7}\]

    Correct Answer: B

    Solution :

    Given that,                 \[\sin x+\cos x=\frac{1}{5}\] On squaring both sides, we get                 \[{{\sin }^{2}}x+{{\cos }^{2}}x+2\sin x\cos x=\frac{1}{25}\] \[\Rightarrow \]               \[\sin 2x=\frac{1}{25}-1=\frac{24}{25}\] Now,     \[\cos 2x=\sqrt{1-{{\sin }^{2}}2x}=\sqrt{1-\frac{576}{625}}\]                 \[=\sqrt{\frac{49}{625}}=-\frac{7}{25}\] \[\therefore \]  \[\tan 2x=\frac{\sin 2x}{\cos 2x}=\frac{-24/25}{-7/25}=\frac{24}{7}\]


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