∫AB = aa 1，∠BAA 1=60

∴△AA 1B is an equilateral triangle.

AB⊥A 1D

CA = CB

∴AB⊥C 1D

AB⊥ Aircraft A 1CD

∴AB⊥A 1C

2) take the midpoint e of B 1C 1 and connect A 1E, CE.

AB = CB = 2

∴a 1b 1=b 1c 1=c 1a 1=a 1c=2

△A 1B 1C 1 is an equilateral triangle.

a 1E =√3/2b 1c 1 =√3

sin∠a 1CE = a 1E/a 1C =√3/2