2. Parallel isosceles angles are equal and two straight lines are parallel.

3, FG, EC are isomorphic angles FG EC.

4、C

5. A.

6、D

7、C

8. solution: AB∑CD

∫≈ 1 = 127 degrees

∴∠EFB= 180 degrees-127 degrees =53 degrees.

∫∠2 = 53 degrees

∴∠FEB=∠2

∴AB∥ CD

9. Solution: MQ∑NP

∠∠BME =∠DNE

∴AB∥CD (same angle, two parallel straight lines)

∫≈ 1 =∠2

∴ ∠EMQ=∠MNP

∴MQ∥NP (same angle, two parallel lines)

10, solution: AB∨CD

∠∠2 =∠EHD

∠ 1=∠2

∴∠ 1=∠EHD (equivalent substitution)

∴AB∥CD (two parallel lines at the same angle)

1 1, (1) solution: EF∑BD

∠∠ADE = 60 degrees, ∠ 1=∠ 2.

∴∠ 1=∠2=30 degree

∫∠3 = 30 degrees.

∴∠ 1=∠3

∴EF∥ BD

(2) Solution: When ∠ABC=∠ AED, that is ∠ABC=60 degrees, DE∨BD.

12、D

13、B

14, parallel

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