由余弦定理cosB=(a^2+c^2-b^2)/2ac=cos(π/4)=>b^2=(根号2)ac=>(sinB)^2=(根号2)sinAsinC (正弦定理)=>sinAsinC=(根号2)/4又cos(A+C)=-(根号2)/2=>cosAcosC=-(根号2)/4=>cos(A-C)=0=>A-C=π/2=>A=5π/8 C=π/8
乓雄歇
