求一到高中三角函数解方程式cos4x﹣cos2x=0
问题描述:
求一到高中三角函数解方程式cos4x﹣cos2x=0
答
cos4x-cos2x=0
2(cos2x)^2-cos2x-1=0
(2cos2x+1)(cos2x-1)=0
cos2x=-1/2或cos2x=1
2x=2kπ-π/3或2x=2kπ+π/3或2x=2kπ
x=kπ-π/6或x=kπ+π/6或x=kπ