SinB*SinC=(CosA/2)^2
SinB*SinC=(1+CosA)/2
2SinB*SinC-CosA=1
而CosA=Cos(180-B-C)=-Cos(B+C)
=-CosBCosC+SinBSinC
CosBCosC+SinBSinC=1
Cos(B-C)=1
B=C
等腰三角形
SinB*SinC=(CosA/2)^2
SinB*SinC=(1+CosA)/2
2SinB*SinC-CosA=1
而CosA=Cos(180-B-C)=-Cos(B+C)
=-CosBCosC+SinBSinC
CosBCosC+SinBSinC=1
Cos(B-C)=1
B=C
等腰三角形