In rectangular trapezoid ABCD, ab ∥ CD, ab ⊥ ad, and ab = 13, CD = 8, ad = 12, then the distance from point a to BC is______ ．

As shown in the figure, the intersection of CE ⊥ AB is e, and the intersection of AF ⊥ BC is f. ∵ in the right angled trapezoid ABCD, ad ⊥ AB, CE ⊥ AB, ≁ DC = AE = 8, ad = CE = 12, then be = ab-ae = 13-8 = 5, ∵ in the right angled triangle BCE, BC = CE2 + be2 = 13. Then AB = CB can be obtained; ∵ {CEB = ∠ AFB = 90 degree, ≌ B is the common angle, ab = CB, ≌ AFB ≌ CEB (AAS), ≌ CE = AF = 12

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1. In the right angle trapezoid ABCD, ab ∥ CD, Da is vertical AB, ab = 13, CD = 8, ad = 12, then what is the distance from point a to BC?
2. As shown in the figure, in the rectangular trapezoid ABCD, the bottom AB = 13, CD = 8, ad ⊥ AB and ad = 12, then the distance from a to BC is () A. 12B. 13C. 12×2113D. 10.5
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5. As shown in the figure, in rectangular trapezoid ABCD, ab ∥ CD, ad ⊥ DC, ab = BC, and AE ⊥ BC. (1) prove: ad = AE; (2) if ad = 8, DC = 4, find the length of ab
6. In rectangular trapezoid ABCD, ab ∥ CD, ad ⊥ DC, ab = BC, and AE ⊥ BC
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