(cos4π\5)*(tan11π\6)*(sin5π\4)

(cos4π\5)*(tan11π\6)*(sin5π\4)

(cos4π\5)*(tan11π\6)*(sin5π\4)=
(cos(π-π\5))*(tan(2π-π\6))*(sin(π+π\4)
=-cos(π\5)*(tanπ\6)*(sinπ\4)
=-√6/6cos(π\5)