18. (The full score of this small question is 12)

(1) As shown in the figure, it is proved that the proposition "A is a straight line in the plane ∏, B is a straight line outside ∏ (B is not perpendicular to ∏), and C is the projection of the straight line B on ∏. If a⊥b, then a⊥c "is true.

(2) Write the inverse proposition of the above proposition and judge whether it is established (without proof).