10th Class Mathematics Introduction to Trigonometry Question Bank Trigonometry

  • question_answer
    If \[A+B+C=180{}^\circ \] , then \[\tan A+\tan B+\tan C\] is equal to

    A) \[2\tan A\,\,\tan B\,\,\tan C\]

    B) \[\tan A\,\,\tan B\,\,\tan C\]

    C) \[\cot A\,\,\cot B\,\,\cot C\]

    D) \[\tan A\,\,\tan B\,\,\cot C\]

    Correct Answer: B

    Solution :

     We know, \[A+B+C={{180}^{o}}\] or            \[A+B={{180}^{o}}-C\] \[\therefore \]                  \[\tan \,(A+B)=tamn\,({{180}^{o}}-C)\] or            \[\frac{\tan A+\tan B}{1-\tan A\tan B}=-\tan C\] or  \[tan\,A+tan\,B=-tan\,C+tan\,A\,tan\,B\,tan\,C\] or \[tan\,\,A+tan\,\,B+tan\,\,C=tan\text{ }A\text{ }tan\text{ }B\text{ }tan\text{ }C\]


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