我来试试吧...（1）sin225=sin(180+45)=-sin45=-√2/2(2) cos4π/3=cos(π+π/3)=-cosπ/3=-1/2(3) sin(-π/3)=-sin(π/3)=-√3/2(4) cos(-7π/6)=-cos(π+-7π/6)=-cos(-π/6)=-cosπ/6=-√3/2