来自胡乃静的问题
已知sin(α-π/4)=7倍根号2/10,cos2α=7/251.求sinα+cosα2.求tan(α+π/3)
已知sin(α-π/4)=7倍根号2/10,cos2α=7/25
1.求sinα+cosα
2.求tan(α+π/3)
1回答
2020-06-24 21:11
已知sin(α-π/4)=7倍根号2/10,cos2α=7/251.求sinα+cosα2.求tan(α+π/3)
已知sin(α-π/4)=7倍根号2/10,cos2α=7/25
1.求sinα+cosα
2.求tan(α+π/3)
1、sin(α-π/4)=7√2/10,展开:sinαcosπ/4-cosαsinπ/4=7√2/10,得,sinα-cosα=7/5(可判断出在第二象限)cos2α=7/25,得2cosαcosα-1=7/25,得cosα=-4/5(4/5不取)所以sinα=3/5得sinα+cosα=3/5+(-4/5)=...