若cos(α-π/3)=12/13,π/3
已知cos(α+β)=12/13,cos(2α+β)=3/5,若β∈(0,π/2),求cosα的值.
计算cos(a+5π/12)cos(a+π/6)+cos(π/12-a)cos(π/3-a)
【紧急求助】计算:cosα+cos(2π/3 +α)+cos(4π/3 +α)
若cos(α-π/3)=12/13,π/3
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).
若cos(α-3π/2)=1/5,求-cosα的值.
数学已知COSα=-12/13 cos(α+β)=17倍根号2/26 且α属于(π,3π/2)
求证:[tan(2π-α)cos(3π/2-α)cos(6π-α)]/[sin(α+3π/2)cos(α+3π/2)]=
cos(2π/3-α)能等于cosα?
已知tan(π+α)=1/3,求cos²(π+α)+sin(π+α)cos(π-α)-2cos²(3
已知(3sinα+cosα)/(3cosα-sinα)=2,则2-3sin(α-3π)sin(1.5π-α)-[cos(