c^2=a^2+b^2-2a*b*conC
=36+16-2*6*4*(-con60)=76
c=根号76＝2根号19
b/sinB＝ c/sinC,sinB＝b*sinC/c
sinB＝[4×(根号3/2)]/2根号19
故 sinB＝根号57/19