已知0<x<派/2<y<派且sin(x+y)=5/131,若tan(x/2)=1/2,分别求cosx及cosy的值2试比较siny与sin(x+y)的大小并说明理由
热心网友
sx=(1-tan(x/2)^2)/(1+tan(x/2)^2)=3/5,sinx=4/5,cos(x+y)=-12/13cosy=cos(x+y-x)=(-12/13)3/5+(5/13)4/5=-16/65. ny0sin(x+y).
已知0<x<派/2<y<派且sin(x+y)=5/131,若tan(x/2)=1/2,分别求cosx及cosy的值2试比较siny与sin(x+y)的大小并说明理由
sx=(1-tan(x/2)^2)/(1+tan(x/2)^2)=3/5,sinx=4/5,cos(x+y)=-12/13cosy=cos(x+y-x)=(-12/13)3/5+(5/13)4/5=-16/65. ny0sin(x+y).