2.( 1)∠ 1 and ∠4 are isomorphic angles.

(2) < 5 and < 3 are internal angles on the same side.

(3) internal dislocation angles of < 2 and <1.

3.( 1)≈ 1 =∠B (two straight lines are parallel and have the same angle)

(2)∠3=∠5 (offset angles are equal and two straight lines are parallel)

(3)∠b+∠BCD = 180； AB//CD (complementary to the inner angle on the same side, with two straight lines parallel)

4.∠ 1=90 ; ∠ 1=60

5. ∠∠ 2 = ∠∠∠ 3 (the top angles are equal)

∵∠ 2 = 72.

∴∠3=72

∵∠ 1= 108

∴∠ 1+∠3= 180

∴AB//CD (the internal angles on the same side are complementary and the two straight lines are parallel)

6.∵AB//DF

∴∠EGB=∠D (two straight lines are parallel and have the same included angle)

∫∠D = 1 15

∴∠EGB=∠D= 1 15

BC//Germany

∴∠ EGB+∠ B = 180 (complementary angles of two parallel lines with internal angles).

∴∠B= 180 -∠EGB=65

Group b

7.

∫AB//DC

∴∠ D+∠ A = 180 (two straight lines are parallel and their internal angles are complementary).

∫ AD//BC

∴∠ D+∠ C = 180 (ditto), ∠ A+∠ B = 180 (ditto).

∴∠D=∠B (equivalent substitution)

8.

Not correct.

Group c

9.

equal division

∴∠ 1=∠EBC= 1/2 ∠ABC

∵∠ 1=∠2∴∠EBC=∠2 (equivalent substitution)

∴DE//BC (offset angles are equal and two straight lines are parallel)

∴∠AED=∠C (two straight lines are parallel and have the same included angle)

∠∠C = 70

∴∠AED=∠C=70

10.( 1) Guess: B'E//DC

∫△ABE is transformed into △AB'E by artificial axisymmetric transformation.

∴△ABE congruence△ AB 'e

∴∠AB'E=∠B (the corresponding angles of congruent triangles are equal).

∠∠B =∠D = 90

∴∠AB'E=∠B=∠D=90

∴B'E//DC (same angle, two parallel lines)

(2)

* B ' e//DC

∴∠ C+∠ B 'EC = 180 (two straight lines are parallel and their internal angles are complementary).

∫∠C = 130

∴∠B'EC= 180 -∠C=50

∫△ABE congruence△ AB 'e

∴∠AEB=∠AEB' (the corresponding angles of congruent triangles are equal).

≈AEB+≈AEB '+≈B ' EC = 180

∴∠AEB=∠AEB'=65