如图，已如平面四边形\(ABCD\)，\(AB=BC=3\)，\(CD=1\)，\(AD=\sqrt{5}\)，\(\angle ADC=90{}^\circ.\)沿直线\(AC\)将\(\vartriangle DAC\)翻折成\(\vartriangle{D}{'}AC\)，则\(\overrightarrow{AC}⋅\overrightarrow{BD}{'}=\)__________；当平面\(D{'}AC{\rm⊥}\)平面\(ABC\)时，则异面直线\(AC\)与\(B{\rm D}{'}\)所成角余弦值是__________.