Overview: 1 questions will be solved this time.Among them
           ☆1 inequalities

[ 1/1Inequality]
    Assignment:Find the solution set of inequality 2cos(1/2a) <1 .
    Question type: Inequality
    Solution:
    The inequality can be reduced to 1 inequality：
        2 * cos ( 1 / 2 * a ) <1         (1)

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    From inequality(1)：
         a < -27.227136 或  -23.038346 < a < -14.660766 或  -10.471976 < a < -2.094395 或  2.094395 < a < 10.471976 或  14.660766 < a < 23.038346 或  a ＞ 27.227136

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    The final solution set is :
         a < -27.227136 或  -23.038346 < a < -14.660766 或  -10.471976 < a < -2.094395 或  2.094395 < a < 10.471976 或  14.660766 < a < 23.038346 或  a ＞ 27.227136
    *Note: Radian.

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