sin11π/6=sin(2π-π/6)
=sin(-π/6)
=-sinπ/6
=-1/2
sin5π/6=sin(π-π/6)
=sinπ/6
=1/2
sin11π/2=sin(6π-π/2)
=sin(-π/2)
=-sinπ/2
=-1sin120怎么算sin120°
=sin(180°-60°)
=sin60°
=√3/2