∠A:∠B=1:2 ∠B=2∠A
a:b=1:根号3
三角形正弦定理:a/sinA=b/sinB=c/sinC 1:根号3 = a/b=sinA/sinB=sinA/(2sinAcosA)
cosA=根号3/2 ∠A=30 ∠B=60 ∠C=90