(1) 根据sinA*sinA+cosA*cosA=1得出sinA=2√5/5 sinB=3√10/10cosc=cos(180-A-B)= -cos(A+B)=-(cosA*cosB-sinA*sinB)=√2/2所以C=45°(2) 根据a/sinA=b/sinB=c/sinC, C=45°即c=√2所以b=3√10/5 , a=4√5/5s=a*b*sinc/2=6/5=1.2
