cos(-α+3/2π)=
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cos(-α+3/2π)=
求证:cos²α+cos²(α+β﹚-2cosαcosβcos﹙α+β﹚=sin²β
cos^2α+cos^2(α+π/3)-cosαcos(α+π/3)化简
已知3sinα-2cosα=0 求 sin^2α- 2sinαcosα+4cos^2α的值
已知sinα+sinβ=2/3且cosα+cosβ=4/3求cos(α-β)的值.谢啦.
不等式证明1已知α、β、γ∈(0,π/2),且tanα+tanβ+tanγ=3,求证:1/(cosαcosβ)+1/(cosβcosγ)+1/(cosγcosα)≥6.
若sin(α-π)=2cos(2π-α),求[sin(π-α)+5cos(2π-α)]/[3cos(π-α)-sin(-α)]的值
已知cosα=1╱3,cos(α+β)=-1╱3,且αβ∈(0,π╱2),则cos(α-β )的值
求和:cos(0)+cos(α)+cos(2α)+cos(3α)+……cos(nα)
已知sinα=15/17 求cos﹙π/3+α﹚,cos﹙3/π-α﹚α属于﹙π/2,π﹚
已知cos(π/6-α),则cos(5π/6+α)×sin(2π/3-α)=
tan(π-α)=2,求(sinα-2cosα)/(3sinα+cosα)的值?
利用诱导公式求三角函数值 cos 6/65π一,利用诱导公式:cos(2kπ+α)=cosα (k∈Z)和cos(π-α)=-cosα 得出cos65π/6=cos(65π/6-10π)=cos(5π/6)=cos(π-π/6)=-cosπ/6=-√3/2二,又或者cos65π/6=cos(11π-1π/6)=-cos(
化简:cosα+cos(2π/3-α)+cos(2π/3+α)
【紧急求助】计算:cosα+cos(2π/3 +α)+cos(4π/3 +α)
4cos²α-2(1+√3)cosα+√3=0
sin(π/2+α)=cosα怎么推导sin(π/2+α)=cosαcos(π/2+α)=-sinαsin(π/2-α)=cosαcos(π/2-α)=sinα都要
cos^3(-π-α)