JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Trigonometrical ratios of sum and difference of two and three angles

  • question_answer
    \[\tan \frac{2\pi }{5}-\tan \frac{\pi }{15}-\sqrt{3}\tan \frac{2\pi }{5}\tan \frac{\pi }{15}\] is equal to

    A) \[-\sqrt{3}\]

    B) \[\frac{1}{\sqrt{3}}\]

    C) 1

    D) \[\sqrt{3}\]

    Correct Answer: D

    Solution :

    We have \[\frac{\tan \frac{6\pi }{15}-\tan \frac{\pi }{15}}{1+\tan \frac{6\pi }{15}\tan \frac{\pi }{15}}=\tan \frac{\pi }{3}\] \[\Rightarrow \,\,\tan \frac{6\pi }{15}-\tan \frac{\pi }{15}=\sqrt{3}+\sqrt{3}\,\tan \frac{6\pi }{15}\tan \frac{\pi }{15}\] \[\Rightarrow \,\,\tan \frac{6\pi }{15}-\tan \frac{\pi }{15}-\sqrt{3}\,\tan \frac{6\pi }{15}\tan \frac{\pi }{15}=\sqrt{3}\].


You need to login to perform this action.
You will be redirected in 3 sec spinner