Prove:

∵ parallel to AO and OE⊥OA.

∴ Quadrilateral AOEB is a rectangle.

∴∠BOE and ∠2 are complementary, while ∠∠ BOE and ∠ 3 are complementary.

∴∠2=∠3

∴∠ 1=∠3 - ①

∠∠ EOH =180-∠AOE-∠1,and ∠ AOE is a right angle.

∴∠EOH and∠1are complementary, and∠ 4 and∠ EOH are known to be complementary.

∴∠ 1=∠4 - ②

Pass conditions ① and ②.

∴∠3=∠4