已知cosα=5/13,3/2π
已知cos(α+β)=12/13,cos(2α+β)=3/5,若β∈(0,π/2),求cosα的值.
已知(2sinα+cosα)/(sinα-3cosα)=-5,则2cos^2α+sin2α
已知cos(π/2+α)=2sin(α-π/2),求[sin^3(π+α)+cos(α+π)]/[5cos(5π/2-α
①化简[sin(2π+α)*cos(7π-α)]/cos(-α)②已知cosθ=-3/5,θ∈(π/2,π),求sin(
已知cos(α-π/3)=12/13,α∈(π/3,π/2),求cosα
1.已知cosα=12/13,α∈(3π/2,2π),求cos(α+π/4).
已知sin(5π-α)=√2cos(3π/2+β),)√3cos(-α)=-√2cos(π+β),0
已知cosα=-3/5,α属于(π/2,2π)则cos(α-π/4)=
1.已知cos(α-β)=12/13,sin(α+β)=-3/5,π/2
已知α.β均为锐角,且cos(α+β)=12/13,cos(2α+β)=3/5,求cosα.
已知cos(π+α)=-5/13,3π/2
已知cosα=1/3,α属于(π,2π),则cosπ/2等于