α、β为锐角sinα=四根号三/7,cos(α+β)= -11/14求sinβ
问题描述：
α、β为锐角sinα=四根号三/7,cos(α+β)= -11/14求sinβ
答
α、β为锐角sinα=4√3/7,cos(α+β)= -11/14求sinβ
sina=4√3/7 ,cosa=1/7
cos(a+b)=-11/14,sin(a+b)=5√3/14
sin(b)
=sin(a+b-a)
=sin(a+b)cosa-sinacos(a+b)
=5√3/14×1/7-4√3/7×(-11/14)
=(5√3+44√3)/(7×14)
=√3/2
b是锐角,所以b=派/3