As shown in the figure, in trapezoidal ABCD, ad is parallel to BC, e is the midpoint of edge CD, and the extension line of AE and BC intersects at point F to judge the relationship between s △ ABF and s trapezoidal ABCD

As shown in the figure, in trapezoidal ABCD, ad is parallel to BC, e is the midpoint of edge CD, and the extension line of AE and BC intersects at point F to judge the relationship between s △ ABF and s trapezoidal ABCD

∵ e is the midpoint of edge CD
∴DE=CE
∵ ad parallel to BC
∴∠ADC=∠DCF,∠DAF=∠AFC
∴△ADE≌△FCE
∴S△ADE=S△FCE
∵ s △ ABF = s quadrilateral AECB + s △ FCE
S trapezoid ABCD = s quadrilateral AECB + s △ ade
S △ ABF = s ladder ABCD