JEE Main & Advanced AIEEE Solved Paper-2010

  • question_answer
      Let \[\cos (\alpha +\beta )=\frac{4}{5}\]and let,\[sin(\alpha -\beta )=\frac{5}{13}\]where\[0\le \alpha ,\beta \le \frac{\pi }{4}\].Then tan\[2\alpha =\]         AIEEE  Solved  Paper-2010

    A) \[\frac{25}{16}\]              

    B)                        \[\frac{56}{33}\]                              

    C) \[\frac{19}{12}\]                              

    D)        \[\frac{20}{7}\]  

    Correct Answer: B

    Solution :

    \[\tan 2\alpha =\tan \left[ (\alpha +\beta )+(\alpha -\beta ) \right]=\frac{\tan (\alpha +\beta )+\tan (\alpha -\beta )}{1-\tan (\alpha +\beta )\tan (\alpha -\beta )}\] as\[\cos (\alpha +\beta )=4/5,\sin (\alpha -\beta )=5/13\] \[\tan 2\alpha =\frac{\frac{3}{4}+\frac{5}{12}}{1-\frac{3}{4}.\frac{5}{12}}=\frac{\frac{9+5}{12}}{\frac{16-5}{16}}=\frac{56}{33}\]


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