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

[ 1/1Inequality]
    Assignment:Find the solution set of inequality cosx <0.9 .
    Question type: Inequality
    Solution:
    The inequality can be reduced to 1 inequality：
         cos x <0.9         (1)

---

    From inequality(1)：
         x < -13.017397 或  -12.115344 < x < -6.734212 或  -√238098509/√7000000 < x < -0.451027 或  0.451027 < x < √238098509/√7000000 或  6.734212 < x < 12.115344 或  x ＞ 13.017397

---

    The final solution set is :
         x < -13.017397 或  -12.115344 < x < -6.734212 或  -√238098509/√7000000 < x < -0.451027 或  0.451027 < x < √238098509/√7000000 或  6.734212 < x < 12.115344 或  x ＞ 13.017397
    *Note: Radian.

Your problem has not been solved here? Please take a look at the  hot problems ！