sin(6/π-a)=1/3sina=
sin(π/6-a)=1/3
cos(π/6-a)=2根号2/3
sina=sin(π/6-π/6+a)=1/2*2根号2/3-根号3/2*1/3
=根号2/3-根号3/6
=(2根号2-根号3)/6