若cos(π+α)=-1/2,3/2π
若cos(α-3π/2)=1/5,求-cosα的值.
已知cosα=1/3,α属于(π,2π),则cosπ/2等于
若cos(π+α)=-1/2,3π/2
若cos(π+α)=-1/2,3/2π
已知cos(π\3-2)=1\3,则cosα+根号3sinα=
cos(2π/3-α)能等于cosα?
cos(-2/3)π=?
(1+sinα+cosα)*[sin(α/2)-cos(α/2)]/√(2+2cosα)化简 (3/2*π
【紧急求助】计算:cosα+cos(2π/3 +α)+cos(4π/3 +α)
已知tan(π+α)=1/3,求cos²(π+α)+sin(π+α)cos(π-α)-2cos²(3
设f(α)=2sinαcosα+cosα/1+sin²α+cos(3π/2+α)-sin²(π/2+
已知tan(3π+α)=2,求:1、(sinα+cosα)²;2、sinα-cosα/2sinα+cosα