(31°51′－25°4′30″）×3＋28°3′÷2
=(31°50′60″－25°4′30″）×3＋28°3′÷2
=6°46′30″×3＋28°3′÷2
=6.775°×3＋28.05°÷2
=34.35°
秒先化为分÷60,再化为度÷60