As shown in the figure, AB is the diameter of ⊙ o, Pb is tangent to ⊙ o at point B, the extension line of chord AC ∥ OP and PC intersects BA at point D, proving that PD is tangent to ⊙ o

As shown in the figure, AB is the diameter of ⊙ o, Pb is tangent to ⊙ o at point B, the extension line of chord AC ∥ OP and PC intersects BA at point D, proving that PD is tangent to ⊙ o

It is proved that: as shown in the figure, connect OC. ∵ AC ∥ OP, ∥ 1 = ∥ 2, ∥ 3 = ∥ 4. ∥ OA = OC, ∥ 1 = ∥ 3. ∥ 2 = ∥ 4. ∥ in △ POC and △ POB, OC = ob ∥ 2 = ∥ 4op = OP, ≌ POC ≌ △ POB (SAS), ∥ PCO = ≌ PbO. ∥ Pb cuts ⊙ o at point B, AB is the diameter of ⊙ o, ∥ PbO =