根据余弦定理：a^2+b^2-c^2=2abcosC又：S=(a²+b²-c²)/(4根号3)∴S=2abcosC/(4根号3)又：S=1/2absinC∴1/2absinC=2abcosC/(4根号3)sinC=cosC/(根号3)tanC=根号3/3C=30°
30º
