已知TANA=-1/2,且A∈(π/2,π),则COS(A+π/4)=
问题描述:
已知TANA=-1/2,且A∈(π/2,π),则COS(A+π/4)=
答
tanA=-1/2,且A∈(π/2,π),则sinA>0,cosA
已知TANA=-1/2,且A∈(π/2,π),则COS(A+π/4)=
tanA=-1/2,且A∈(π/2,π),则sinA>0,cosA