Vertical relationship If PA ⊥ BC, Pb ⊥ AC, then the projection of point P on plane ABC is ⊥ ABC_____ 2. P is a point outside the plane where △ ABC is located. If PA = Pb = PC, then the projection of P on the bottom surface is____ 3. Given that three line segments intersect at the same point P, the line segments PA, Pb and PC are perpendicular, and a, B and C are in the same plane, P is outside the plane ABC, and pH is perpendicular to the plane ABC at h, then the perpendicular foot h is △ ABC____ (inner / central / perpendicular / outer) 4. In the cube abcd-a1b1c1d1, e and F are the midpoint of edge Aa1 and CC1, respectively Please use the three perpendicular theorem to solve the fourth question in detail

Vertical relationship If PA ⊥ BC, Pb ⊥ AC, then the projection of point P on plane ABC is ⊥ ABC_____ 2. P is a point outside the plane where △ ABC is located. If PA = Pb = PC, then the projection of P on the bottom surface is____ 3. Given that three line segments intersect at the same point P, the line segments PA, Pb and PC are perpendicular, and a, B and C are in the same plane, P is outside the plane ABC, and pH is perpendicular to the plane ABC at h, then the perpendicular foot h is △ ABC____ (inner / central / perpendicular / outer) 4. In the cube abcd-a1b1c1d1, e and F are the midpoint of edge Aa1 and CC1, respectively Please use the three perpendicular theorem to solve the fourth question in detail

1. Point a (I see these points in the cube) 2. The center of circumscribed circle of triangle ABC, let p be mapped o ∵ P on the bottom and O ∵ Po ⊥ Ao, Po ⊥ OC, Po ⊥ OB and ∵ PA = Pb = PCPO = Po ≌ apo ≌ POB ≌ POC ≌ Ao = ob = OC3