(1)行租cosB=2cos²B/2-1=3/5sinB=√(1-cos²B)=4/5sinA=sin(B+C)=sinBcosC+sinCcosB=4/5*√2/2+3/5*√2/2=7√2/10(2)信差由正弦定理b/sinB=a/sinA∴b=asinB/sinA=8√2/7∴S=(1/滑带皮2)*absinC=8/7