Seventh grade mathematics, book 2, chapter 5, problem solving! !

Solution: (1)≈ 1 = 30, ABAC (2) ≈ BAC = 90, ∠ B = 60.

∴∠bad= 120 ∴∠acb= 180-∠BAC-∠b = 30

∠∠B = 60∠∠ 1 = 30

∴∠dab+∠b= 120+60 = 180 ∴∠ 1=∠acb

∴AD∥BC (internal dislocation angles are equal and two straight lines are parallel)

I hope this helps ∵∠ ba d +∠ b =120+60 =180.

∴AB∥CD (complementary to the inner angle on the same side, with two straight lines parallel)