几道三角函数数学题.半小时内给答案.
1.已知tan(α-β)=1/2tanβ=-1/7且α.β属于(0,π)求2α-β的值
2.已知αβ属于(-π/2,π/2)且tanαtanβ是方程x2+3根号3x+4=0的两根α+β的值?
Aπ/3或者-2π/3B-2π/3C-arctan3根号3/5Dπ-arctan3根号3/5
3.若sinA+cosA/sinA-cosA=2.则sin(A-5π)sin(3π/2-A)=...
4..已知α.β属于(3π/4,π),sin(α+β)=-3/5,sin(β-π/4)=12/13则cos(α+π/4)=?