Through observation and analysis, this problem should be verified by judging DE⊥AC and BC⊥AB first, and then fg∑CD.

answer

Solution:

Evidence: because DE⊥AC, BC⊥AB.

So ∠ AED = ∠ ACB = 90 degrees,

So in BC, Germany∨

So < 2 = < 3.

Because < 1 = < 2.

So < 1 = < 3.

So fg sigma CD

Because FG⊥AB

So ∠ FGB = 90 degrees, ∠ CDB = ∠ FGB = 90 degrees.

Namely CD⊥AB

So the answer is:

leave out

comment

This question examines the determination of parallel lines. Correctly identifying congruent angle, inner angle and inner angle of the same side in "three-line octagon" is the key to correct answer. If you can't meet angles with equal or complementary relationships, you will mistakenly think that there is a parallel relationship. Only when congruent angles and internal angles are equal and the internal angles on the same side are complementary, can you deduce that two sections are parallel.