余弦y=cosx,x∈[-π/2,3π/2]的五个关键点
问题描述：
余弦y=cosx,x∈[-π/2,3π/2]的五个关键点
答
五个关键点为
x=-π/2,y=cosx=cos(-π/2)=0
x=0,y=cosx=cos(0)=1
x=π/2,y=cosx=cos(π/2)=0
x=π,y=cosx=cos(π)=-1
x=3π/2,y=cosx=cos(3π/2)=0