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

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

Extend the intersection point of CM and DA at E. ∵ ad ∥ BC, ∵ Mae = ∥ B, ∥ e = ∥ BCM. Am = BM, ≌ ame ≌ BMC. ∥ me = MC = 6.5, AE = BC. BC + CD + Da = 17, ∥ d = 90 °, de + DC = 17 ①, de2 + DC2 = CE2 = 169 ②. ∥ de · CD = 12 [(de + DC) 2-de2-dc2] = 60. ∥ the area of trapezoidal ABCD is 12de · CD = 30

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 point of CE ⊥ AB is e, and the intersection point 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

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 point of CE ⊥ AB is e, and the intersection point 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