已知sinB=1/3,sin(A+B)=1,求sin(2A+B)的值.
问题描述:
已知sinB=1/3,sin(A+B)=1,求sin(2A+B)的值.
答
sin(A+B)=1,cos(A+B)=0
sinB=1/3,
sin(2A+B)=sin[(A+B)+A]
=sin(A+B)cosA+cos(A+B)sinA
=cosA+0
=cos[(A+B)-A]
=cos(A+B)cosA+sin(A+B)sinA
=0+sinA
=1/3