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

As shown in the figure, the intersection of CE ⊥ AB is e, and the intersection of AF ⊥ BC is f. ∵ in right angled trapezoid ABCD, ad ⊥ AB, CE ⊥ AB, ≁ DC = AE = 8, ad = CE = 12, then be = ab-ae = 13-8 = 5, ∵ in 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. It is known that in the trapezoidal ABCD, ad ‖ BC, AB: BC: CD: Da = 4:5:3:2, if BC-AD = 9, the lengths of AB and DC are obtained
2. 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
3. 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
4. In rectangular trapezoid ABCD, ab ∥ CD, ad ⊥ DC, ab = BC, and AE ⊥ BC
5. As shown in the figure, in the trapezoidal ABCD, AD / / BC, ∠ ABC = 60 °. ∠ DCB = 30 ° AB = 4, find BC ad
6. Trapezoid ABCD is right angle trapezoid, AB / / DC, ∠ DAB = 90 °, PA ⊥ plane ABCD, and PA = ad = DC = & frac12; ab = 1, M is the midpoint of Pb, find the dihedral angle formed by plane AMC and plane BMC
7. As shown in the figure, in rectangle ABCD, ab = 3, BC = 4, e is the moving point on edge ad, f is a point on ray BC, EF = BF and intersecting ray DC at point G, let AE = x, BF = y (1) When △ bef is an equilateral triangle, find the length of BF (2) Find the analytic expression of the function between Y and X, and write out its domain of definition (3) Fold △ Abe along the straight line be, and point a falls at a '. Try to explore whether △ a'bf can be an isosceles triangle? If so, ask for the length of AE; if not, explain the reason As long as the answer and steps of the third question
8. In rectangular ABCD, ab = 4, ad = 2, point m is the midpoint of AD. point E is a moving point on edge ab. connect EM and extend the intersection line CD at point F, cross m to make the vertical line of EF, the extension line of BC at point G, connect eg, and the intersection side DC at point Q. let the length of AE be x and the area of triangle EMG be y (1) Find the tangent value of ∠ MEG; (2) Find the analytic expression of Y with respect to x, and write out the value range of X; (3) The midpoint of Mg is denoted as point P and connected with CP. if {PGC} efq, find the value of Y
9. Known: as shown in the figure, in trapezoidal ABCD, AB is parallel to CD, AC is vertical to BC, ad is vertical to BD, e is the midpoint of AB, prove: angle ECD is equal to angle EDC
10. In the quadrilateral ABCD, BD is perpendicular to ad, AC is perpendicular to BC, e is the key point of AB, and the verification angle EDC = angle ECD Wait online. It's urgent
11. 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?
12. In rectangular trapezoid ABCD, ab ∥ CD, ab ⊥ ad, and ab = 13, CD = 8, ad = 12, then the distance from point a to BC is______ ．
13. As shown in the figure, in ladder ABCD, AB is parallel to DC, point E is the midpoint of DC, ∠ AED = ∠ BEC, proving that ladder ABCD is isosceles ladder
14. As shown in the figure, in trapezoidal ABCD, ∠ d = 90 ° and M is the midpoint of ab. if cm = 6.5 and BC + CD + Da = 17, the area of trapezoidal ABCD is () A. 20B. 30C. 40D. 50
15. In trapezoidal ABCD, if ab ‖ CD, point E is the midpoint of AD and s △ BEC = 2, then the area of trapezoidal ABCD is______ ．
16. In ladder ABCD, AD / / BC, DC / / BC, e are the midpoint of ab It's BC ⊥ DC
17. As shown in the figure, ladder ABCD, e is the midpoint of AB, DC = AD + BC, prove de ⊥ EC
18. In the trapezoidal ABCD, ab ‖ CD, ∠ a = 90 °, ab = 2, BC = 3, CD = 1, e is the midpoint of AD. try to judge the position relationship between EC and EB, and write the inference
19. In the isosceles trapezoid ABCD, AD / / BC, AB / / DC, point E is a point in the trapezoid, and EA = ed, EB = EC is proved
20. As shown in the figure, in trapezoidal ABCD, ad ∥ BC, ab = DC, AE ⊥ BC at point E, the vertical bisector GF of AB intersects BC at point F, intersects AB at point G, and connects AF. it is known that ad = 1.4, AF = 5, GF = 4. (1) calculate the waist length of trapezoidal ABCD; (2) calculate the area of trapezoidal AFCD