Gao, HaiyinWeng, ShiyouJiang, DaqingHou, Xuezhang2021-07-152021-07-152006-02-28Gao, H., Weng, S., Jiang, D., & Hou, X. (2006). On second order periodic boundary-value problems with upper and lower solutions in the reversed order. <i>Electronic Journal of Differential Equations, 2006</i>(25), pp. 1-8.1072-6691https://hdl.handle.net/10877/13898In this paper, we study the differential equation with the periodic boundary value u″(t) = ƒ(t, u(t), u′(t)), t ∈ [0, 2π] u(0) = u(2π), u′(0) = u′(2π). The existence of solutions to the periodic boundary above with appropriate conditions is proved by using an upper and lower solution method.Text8 pages1 file (.pdf)enAttribution 4.0 InternationalPeriodic boundary valueExistenceUpper and lower solutionsArticle