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