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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