According to the meaning of the question, DE⊥BF, AB⊥BF

Because ∠ DCE = 45

So ce = de = CD/√ 2 = 2/√ 2 = √ 2 (m)

Because "the shadow length of the 1m pole measured by the sun at a certain moment is 2m".

Therefore, according to the similarity principle, ef = 2de = 2 √ 2 (m) and BF = 2ab are obtained.

Because BC = 10 (m)

So BF = 10+3 √ 2 (m)

So ab = 5+3 √ 2/2 (m)

(If the approximate value is taken, AB≈7. 12(m))

Jiangsu Wu Yunchao wishes you academic progress.