11th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-7

  • question_answer
    The value of \[\mathbf{tan}{{\mathbf{1}}^{{}^\circ }},\mathbf{tan}{{\mathbf{2}}^{{}^\circ }},\mathbf{tan}{{\mathbf{3}}^{{}^\circ }}...\mathbf{tan}\text{ }\mathbf{8}{{\mathbf{9}}^{{}^\circ }}\]is equal to:

    A)  0                   

    B)  \[-1\]             

    C)  \[~-2\]                         

    D)  1

    Correct Answer: D

    Solution :

    [d] \[\because y=tan{{1}^{{}^\circ }}.\,tan{{2}^{{}^\circ }}.\text{ }tan{{3}^{{}^\circ }}.\text{ }tan{{4}^{{}^\circ }}.....tan{{89}^{{}^\circ }}\] \[=tan{{1}^{{}^\circ }}.\text{ }tan\left( {{90}^{{}^\circ }}-{{1}^{{}^\circ }} \right).tan{{2}^{{}^\circ }}.\text{ }tan\left( {{90}^{{}^\circ }}-2 \right).....tan{{45}^{{}^\circ }}\]\[=tan{{1}^{{}^\circ }}.\text{ }cot{{1}^{{}^\circ }}.\text{ }tan{{2}^{{}^\circ }}.\text{ }cot{{2}^{{}^\circ }}......\text{ }tan{{.45}^{{}^\circ }}\] \[=1\times 1\times 1..........\times 1=1\]


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