1.若(1+tanx)/(1-tanx)=3+2根号2,则tan(x- π/4)=?2.已知sin(a-b)cosa-cos(a-b)sina=4/5,那么cos2b=?

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/29 08:06:47

1.若(1+tanx)/(1-tanx)=3+2根号2,则tan(x- π/4)=?2.已知sin(a-b)cosa-cos(a-b)sina=4/5,那么cos2b=?
1.若(1+tanx)/(1-tanx)=3+2根号2,则tan(x- π/4)=?
2.已知sin(a-b)cosa-cos(a-b)sina=4/5,那么cos2b=?

1.若(1+tanx)/(1-tanx)=3+2根号2,则tan(x- π/4)=?2.已知sin(a-b)cosa-cos(a-b)sina=4/5,那么cos2b=?
1、tan(x-π/4)=(tanx-1)/(1+tanx)=-1/(3+2√2)=2√2-3;
2、已知式化为sin(a-b-a)=4/5,即sinb=-4/5,
那么cos2b=1-2sin²b=1-2(-4/5)²=1-32/25=-7/25.