已知函数y=Asin(ωx+ψ),x∈R(其中A>0,ω>0)的图象,用“”求其解析式,其依据就是“五点法”作函数y=Asin(ωx+ψ)图象思维的逆向应用。利用此法只须仔细观察一个周期内形如图1的图象。然后对照图中“五点”横坐标所满足的条件,便可求出ψ,从而求出函数y=Asin(ωx+ψ)的解析式。如图1,Xi(i=1,2,3,4,5)(其中,X_1一定是图中“五点”的第一个关键点)满足: It is known that the image y = Asin (ωx + ψ), x∈R (where A> 0, ω> 0) is solved by “”, which is based on the “five point method” Function y = Asin (ωx + ψ) Reverse application of image thinking. Use this method only carefully observe the shape of a cycle as shown in Figure 1 image. Then, by contrast with the condition of the abscissa of “five o’clock” in the graph, ψ can be obtained to get the analytic formula of function y = Asin (ωx + ψ). As shown in Figure 1, Xi (i = 1, 2, 3, 4, 5) (where X_1 must be the first key of “five points” in the figure)