c=2RsinC, sinC=c/2Rb=2RsinB, sinB=b/2RsinC=2√3sinB, c/2R=2√3*b/2Rc=2√3ba^2=b^2+c^2-2bc*cosAa^2-b^2=c^2-2bc*cosA√3bc=c^2-2bc*cosA√3b*2√3b=12b^2-2b*2√3b*cosA6b^2=12b^2-4√3b^2cosAcosA=√3/2A=30
