余弦定理可得：c²=a²+b²-2abcosC=1/2 c=√2/2正弦定理可得：c/sinc=a/sina=b/sinb=√2sinA=√2/2 sinB=(√6-√2)／4 当A=45º时 B=105º sinB=sin75=sin（45+30）=(√6+√2)／4,与原题不符∴...