1.4sin^2Ccos^2C+2sin^2C*cosC=2sin^2C 2cos^2C+cosC-1=0 cosC=1/2 C=602.余弦定理a^2+b^2-2abcosC=c^2 cosC=1/2则(a+b)^2-3ab=c^2 ab=6 S=1/2sinC ab=二分之三倍根号三