As shown in the figure, ▱ the diagonal lines AC and BD of ABCD intersect at point O, point E is the midpoint of CD, and the perimeter of △ abd is 16cm, then the perimeter of △ DOE is______ cm．

As shown in the figure, ▱ the diagonal lines AC and BD of ABCD intersect at point O, point E is the midpoint of CD, and the perimeter of △ abd is 16cm, then the perimeter of △ DOE is______ cm．

∵ quadrilateral ABCD is a parallelogram, ≌ o is the midpoint of BD, ≌ abd ≌ CDB, and ≌ e is the midpoint of CD, ≌ OE is the median line of △ BCD, ≌ OE = 12bc, that is, the perimeter of △ DOE = 12 △ BCD, ≌ DOE = 12 △ DAB. ≌ DOE = 12 × 16 = 8cm

As shown in the figure, in RT triangle ABC, the angle ACB = 90 degrees, be bisector angle ABC intersects AC at point E, point D is on AB, De is perpendicular to EB

(1) Because angle CEB is equal to angle EDB is equal to 60 degrees, angle AEB is equal to angle ade because angle a is the common angle of triangle AEB and triangle ade, and AE is the common edge of triangle AEB and triangle ade, so according to the principle of angle, triangle AEB is similar to triangle ade. (2) BC is 6

It is known that the triangle ABC and the triangle ade are two isosceles triangles whose base is on the same straight line, as shown in the figure
Synchronous exercise page 42 question 5

It is proved that ∵ ABC is isosceles triangle ∵ AB = AC ∠ B = ∠ C ∵ ade is isosceles triangle ∵ ad = AE ≌ abd ≌ AEC ∵ BD = EC ∵ BD + de = EC = de ≌ CD = be

Known: as shown in the figure, triangle ABC, ∠ 1 = ∠ 2, de parallel AB, prove that the triangle ade is isosceles triangle

In ∵ △ ABC, if ∵ B = ∵ C, ad is vertical and bisects BC, then ab ∥ De, that is, de ⊥ AC, (∵ DAE = ∵ ade = 90 °) ∥ ade is isosceles triangle