证明cos^4A=1/4+cos2A+1/4cos^2A

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/15 08:39:35

证明cos^4A=1/4+cos2A+1/4cos^2A
证明cos^4A=1/4+cos2A+1/4cos^2A

证明cos^4A=1/4+cos2A+1/4cos^2A
(cosA)^4=[(cosA)^2}^2=[(1+cos2A)/2]^2
=1/4+cos2A+(cos2A)^2 得证