Question

在△ABC中,已知A,B,C所对的边分别为a,b,c若(sinA)^2+sinAsinB=(sinC)^2-(sinB)^2,则角C等于多少

求详细过程

Answer 1

cosC=(a²+b²-c²)/(2ab)=(sin²A+sin²B-sin²C)/(2SinASinB)=-1/2
C=120°