(2)①22.5

②∫aa 1 = a l a 2 = a 2 a 3 = 1，A l A 2 ⊥A 2 A 3

∴A l A 3 =，AA 3 = 1+

∫a2 a3 ⊥a 3 a4，

∴A Los Angeles 2 // A 3 A 4

Similarly, A 3 A 4 // A 5 A 6

∴∠A= ∠AA 2 A 1 =∠AA 4 A 3 =∠AA 6 A 5

∴AA 3 = A 3 A 4，AA 5 =A 5 A 6

∴a 2 = A 3 A 4 =AA 3 = 1+

a 3 =AA 3 + A 3 A 5 = a 2 +A 3 A 5

A 3 A 5 = a 2？

∴ a 3 =A 5 A 6 = AA 5 = a 2 + a 2 =( + 1) 2 .