10th Class Mathematics Introduction to Trigonometry Question Bank Trigonometry

  • question_answer
    If \[\tan \theta =\frac{3}{4}\] and \[0<9,\,<90{}^\circ \], then the value of \[\sin \theta \cos \theta \]

    A) \[\frac{1}{5}\]

    B) \[\frac{9}{5}\]

    C) \[\frac{12}{25}\]

    D) \[\frac{25}{12}\]

    Correct Answer: C

    Solution :

     Given,    \[\tan \theta =\frac{3}{4}\] \[\therefore \]  \[\sec \theta =\sqrt{1+{{\tan }^{2}}\theta }\]                 \[=\sqrt{1+\frac{9}{16}}=\sqrt{\frac{25}{16}}=\frac{5}{4}\] or            \[\cot \theta =\frac{4}{5}\] \[\therefore \]  \[\sin \theta \,\cos \theta =\tan \theta .{{\cos }^{2}}\theta \]                 \[=\frac{3}{4}\times \frac{16}{25}=\frac{12}{25}\]


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