-11π/4=4π-11π/4=5π/4=π+π/4，sin(-11π/4)=sin(π+π/4)=-sinπ/4=-√2/2，tan(-11π/4)=tan(π+π/4)=tanπ/4=1，cos(-11π/4)=cos(π+π/4)=-cosπ/4=-√2/2，
供参考。
