Question

（高一数学）已知Sin（A＋B）＝1,求证Sin（2A＋B）＝SinB

Answer 1

Sin(2A+B)=sin[A+(A+B)]=sinAcos(A+B)+COSAsin(A+B)

-->sin(A+B)=1 A+B=90,cos(A+B)=0

=cosA*1=cos(90-B)=SinB