sin(-5/3π)＝－sin5π/3＝－sin(2π－π/3)＝sinπ/3 tan(632°24')＝tan(720－87°36')＝tan(－87°36')＝－tan87°36' tan17π/6＝tan(2π＋5π/6)＝tan5π/6＝tan(π－π/6)＝－tanπ/6
