14.如图1,在菱形ABCDABCDABCD中,∠ABC=60∘\angle ABC=60\circ∠ABC=60∘,将ΔABC\Delta ABCΔABC沿着ACACAC翻折至如图2所示的△AB1CAB_{1}CAB1C的位置,构成三棱锥B1−ACDB_{1}-ACDB1−ACD.(1)证明:AC⊥B1DAC\bot B_{1}DAC⊥B1D.(2)若平面ACB1⊥ACB_{1}\botACB1⊥平面ACDACDACD,求B1CB_{1}CB1C与平面AB1DAB_{1}DAB1D所成角的正弦值.