1 It is known that AD is the center line of triangle ABC, AE is perpendicular to AB, AF is perpendicular to AC, and AE=AB, AF=AC.

Verification: AD= half EF

(e, f are all outside the triangle ABC, and AEF also forms a triangle)

2. a point d in the equilateral triangle ABC, BD=AD.

PB=AB，∠DBP=∠DBC，

Find the degree of ∠BPD

(P is a point outside AC, and PDB also forms a triangle)

3. In the triangle ABC, ∠BAC = 2 ∠ b. AB=2AC .AE is the bisector of ∠ BAC.

Prove that ∠C is a right angle.

(e) In CB, you can use truncation to make up for your own shortcomings)

4. In the triangle ABC, AD bisects ∠BAC, CE is perpendicular to AD and EF‖BC.

Verification: CE divides the Fed equally.

(e is on AB, even ED)