As shown in the figure, we know that be ⊥ ad, CF ⊥ ad, and be = cf. please judge whether AD is the middle line of △ ABC or the angular bisector? Please state the reason for your judgment

Ad is the middle line of △ ABC. The reasons are as follows: ∵ be ⊥ ad, CF ⊥ ad, ∵ bed = ≌ CFD = 90 ° in △ BDE and △ CDF, ∵ bed = & nbsp; ≌ cdfbe = CF ≌ BDE ≌ CDF (AAS), ≌ BD = CD

RELATED INFORMATIONS

1. As shown in the figure, the midlines AD and be of △ ABC intersect at point F. what is the quantitative relationship between △ ABF and the area of quadrilateral cefd? Why?
2. As shown in the figure, ad is the middle line of △ ABC, AE: AC = 1:3, ad intersects be at point F, then the ratio of the area of △ ABC to the area of △ ABF is one
3. BD score ∠ ABC, be score ∠ ABC is 2:5, DBE = 21 degrees, calculate the degree of ∠ ABC
4. As shown in the figure, BD is divided into two parts, be is divided into ABC 2:5, DBE = 21 ° and the degree of ABC is calculated
5. As shown in the figure, BD bisects ∠ ABC, be bisects ∠ ABC into two parts of 2:5, ∠ DBE = 27 ° and calculates the degree of ∠ ABC
6. BD bisects the angle ABC, be divides the angle ABC into 3:5, two parts, the angle DBE is equal to 15 degrees, and finds the degree of the angle ABC
7. BD bisects ∠ ABC, be divides ∠ ABC into two parts of 3:4, ∠ DBE = 8 degrees, and calculates the degree of ∠ ABC
8. It is known that ad is the bisector of the outer angle EAC of △ ABC, and ad ‖ BC, then the edge of △ ABC must satisfy______ ．
9. As shown in the figure, △ ABC, ab = AC, ad ‖ BC, then ad bisects ∠ EAC, try to explain the reason
10. As shown in the figure, it is known that ∠ B = ∠ C. If ad ‖ BC, does ad divide ∠ EAC equally? Please give reasons
11. As shown in the figure, in △ ABC, ab = AC, ad ⊥ BC at point D, point E on AC, CE = 2ae, ad = 9, be = 10, ad and be intersect at point F, then the area of △ ABC is______ ．
12. Triangle ABC, ab = AC, ad vertical BC, CECF are the triangles with ACB = 48 degrees intersecting ad at e, F, connecting be intersecting AC at g, and calculate the degree of angle AGF
13. As shown in the figure, in △ ABC, EF is the median line of △ ABC, D is a point on the side of BC (not coincident with B and C), ad and EF intersect at point O to connect de and DF. To make quadrilateral AEDF a parallelogram, conditions need to be added______ (only add one condition, the answer is not unique)
14. In the triangle ABC, ab = AC, D is the midpoint of AB, de ⊥ AB intersects AC at point E, the circumference of the triangle BCE is known to be 10, and ac-bc = 2, so the circumference of the triangle EBC can be obtained
15. In the triangle ABC, ab = AC, D is the midpoint of AB, De is perpendicular to AB, AC intersects with E, the circumference of EBC is known to be 10, and ac-bc = 1 The circumference of ABC
16. As shown in the figure, in △ ABC, AE is the angular bisector, and ∠ B = 52 °, C = 78 ° to find the degree of ∠ AEB
17. As shown in the figure, in △ ABC, AE is the angular bisector, and ∠ B = 52 °, C = 78 ° to find the degree of ∠ AEB
18. As shown in the figure, in △ ABC, AE is the angular bisector, and ∠ B = 52 °, C = 78 ° to find the degree of ∠ AEB
19. As shown in the figure, a, P, B and C are four points on the circle O, angle APC = angle CPB = 60 degrees. Judge the shape of triangle ABC and prove it
20. ① Let the three sides of △ ABC be a, B and C respectively, and try to prove that: a < 12 (a + B + C). ② let the four sides of a quadrilateral be a, B, C and D in turn, and the two diagonals be e and f respectively, and prove that: e + F > 12 (a + B + C + D)