Question

高中数学问题。在线等！！！！！！！！

c2+b2/c2-b2=Sin(C+B)/Sin(C-B),判断△ABC的形状

Answer 1

c2+b2/c2-b2=Sin(C+B)/Sin(C-B),

(c2+b2)Sin(C-B)=(c2-b2)Sin(C+B)

b2(Sin(C+B)+Sin(C-B))=c2(Sin(C+B)-Sin(C-B))

2b^2sinCcosB=2c^2sinBcosC,正弦定理

2sin^2BsinCcosB=2sin^2CsinBcosC

2sinBcosB=2sinCcosC,sin2B=sin2C

2B=2C,2B+2C=180,等腰或直角