cos²α+cos²(120°-α)+cosαcos(120°-α)化简
化简:cos(-π-α)
化简cos(π/4-α)²+cos(π/4+α)²
化简(sinα+cosα)²+(sinα-cosα)²
化简cos(π/12)*cos(5π/12)
化简cos平方α+cos平方(α-π/3)+cos平方(α+π/3) 急、~
【紧急求助】计算:cosα+cos(2π/3 +α)+cos(4π/3 +α)
化简cosα+cos(120°-α)+cos(120+α)
求证:cos²α+cos²(α+β)-2cosαcosβcos(α+β)=sin²2β
化简[sin(π/2-α)cos(π/2-α)]/cos(π+α)-[sin(π-α)cos(π/2-α)]/sin(π
化简:{sin^2(α+π)*cos(α+π)*cos(-α-2π)}/{sin(-α-2π)*tan(π+α)*cos
已知tan(π+α)=1/3,求cos²(π+α)+sin(π+α)cos(π-α)-2cos²(3