Solve the equation cosx= -0.4 on the interval 0≤x<2π.

问题描述:

Solve the equation cosx= -0.4 on the interval 0≤x<2π.

cosx = -0.4arccos(-0.4) ≈ 1.98 radiansx = 2nπ±arccos(-0.4),n can be any integern = 0:x = 2nπ+arccos(-0.4) = 1.98n = 1:x = 2nπ-arccos(-0.4) = 2π - 1.98 = 4.30