According to the properties of trigonometric functions, we can get. The decreasing range of sine function is [π/2+2kπ, 3π/2+2kπ], and the decreasing range of cosine function is [2kπ, π+2kπ]. Substituting the function into the decreasing interval (for example, y=sin(ωx+ φ) means substituting the formula ωx+ φ into the decreasing interval corresponding to the sine function, and the positive solution can be obtained.