cos(α-½β)=-三分之一,sin(½α-β)=¼,且.cos(α-½β)=-三分之一,sin(½α-β)=¼,且二分之三派<α<2派,½派小于β<π,求cos二分之一(α+β)
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![cos(α-½β)=-三分之一,sin(½α-β)=¼,且.cos(α-½β)=-三分之一,sin(½α-β)=¼,且二分之三派<α<2派,½派小于β<π,求cos二分之一(α+β)](/uploads/image/z/112530-66-0.jpg?t=cos%28%CE%B1-%26%23189%3B%CE%B2%29%3D-%E4%B8%89%E5%88%86%E4%B9%8B%E4%B8%80%2Csin%28%26%23189%3B%CE%B1-%CE%B2%29%3D%26%23188%3B%2C%E4%B8%94.cos%28%CE%B1-%26%23189%3B%CE%B2%29%3D-%E4%B8%89%E5%88%86%E4%B9%8B%E4%B8%80%2Csin%28%26%23189%3B%CE%B1-%CE%B2%29%3D%26%23188%3B%2C%E4%B8%94%E4%BA%8C%E5%88%86%E4%B9%8B%E4%B8%89%E6%B4%BE%EF%BC%9C%CE%B1%EF%BC%9C2%E6%B4%BE%2C%26%23189%3B%E6%B4%BE%E5%B0%8F%E4%BA%8E%CE%B2%EF%BC%9C%CF%80%2C%E6%B1%82cos%E4%BA%8C%E5%88%86%E4%B9%8B%E4%B8%80%EF%BC%88%CE%B1%2B%CE%B2%EF%BC%89)
cos(α-½β)=-三分之一,sin(½α-β)=¼,且.cos(α-½β)=-三分之一,sin(½α-β)=¼,且二分之三派<α<2派,½派小于β<π,求cos二分之一(α+β)
cos(α-½β)=-三分之一,sin(½α-β)=¼,且.
cos(α-½β)=-三分之一,sin(½α-β)=¼,且二分之三派<α<2派,½派小于β<π,求cos二分之一(α+β)
cos(α-½β)=-三分之一,sin(½α-β)=¼,且.cos(α-½β)=-三分之一,sin(½α-β)=¼,且二分之三派<α<2派,½派小于β<π,求cos二分之一(α+β)
cos(α-½β)=-1/3,sin(½α-β)=¼,3/2π<α<2π,½π小于β<π,求cos1/2(α+β)
令α-½β=A ½α-β=B 则1/2(α+β)=A-B
3/2π<α<2π,½π<β<π
3/4π<1/2α<π,-1/2π<-1/2β<-1/4π ,- π<-β<-½π
π<A=α-½β<7/4π ,-1/4π<½α-β=B<1/2πcosA=-1/3
sinA=- 自己算吧
sinB=1/4 cos=
cos(A-B)=cosAcosB+sinAsinB