As shown in the figure, △ ABC, ab = AC, D, e and F are the points on AB, BC and Ca respectively, and BD = CE, ∠ def = ∠ B

It is proved that: ∵ Dec = ∵ B + ∵ BDE = ∵ CEF + ∵ def, ∵ def = ∵ B, ∵ CEF = ∵ BDE. ∵ AB = AC, ∵ C = ∵ B. in △ BDE and △ CEF, ? B = ? CBD = CE ≌ BDE = ≌ CEF (ASA). ≌ de = Fe. So △ DEF is isosceles triangle

RELATED INFORMATIONS

1. Three points a (0,2,3), B (- 2,1,6), C (1, - 1,5) are known. If | a | = √ 3, and a is perpendicular to ab vector and AC vector respectively, then
2. Can we use parallelogram and triangle rules as long as it is a vector? Such as the title
3. (my blank space is to let you see the title better, and it is required to make simple calculation! I am very urgent! Do as much as you can.) 1. 1 + 2 of 1 + 1 + 2 + 3 of 1 + 1 + 2 + 3 + 4 of 1 + 1+2+… One in 99= 2. (1 / 11 + 1 / 21 + 1 / 31 + 1 / 41) * (1 / 21 + 1 / 31 + 1 / 41 + 1 / 51) - (1 / 11 + 1 / 21 + 1 / 31 + 1 / 41 + 1 / 51) * (1 / 21 + 1 / 31 + 1 / 41 + 1 / 51)= 471471471471÷157157157157=
4. The function formula of the price f (T) of a commodity in the last 30 days f (T) = t + 8 (0
5. Given the function f (x) = ax-b / x-2lnx, f (1) = 0, Given the function f (x) = ax-b / x-2lnx, f (1) = 0 (1) If the function f (x) is a monotone function in its domain of definition, the value range of real number a is obtained (2) The slope of the tangent line of the image at x = 1 is 0, a (n + 1) = f '(1 / an + 1) - Nan + 1. If A1 > = 3, it is proved that an > = n + 2
6. Vector a = (x1, Y1), vector b = (X2, Y2), a + B = (x1 + X2, Y1 + Y2), how to express a * B, is it equal to a + B
7. A rectangle is one fourth of a meter long and two fifths of a meter wide. Its perimeter is () meters and its area is () square meters
8. The perimeter of the rectangle is 10 meters, and the width is two fifths of the length. The area of the rectangle is () square meters, which can be used as a fraction
9. A rectangle is five fifths of its length and three fifths of its width. What is its perimeter and area?
10. The area of the rectangle is 2 / 5 square meters, and the area of the shadow part is 2 / 5 of the area of the rectangle
11. The problem in the program diagram of solving inequality ax + b > 0 1： Input a, B 2: a > 0? 3: Yes, output x > - B / a no, output X
12. In the square ABCD, e is the midpoint of BC, f is the point on CD, and CF = 14CD, try to judge whether △ AEF is a right triangle? Try to explain the reason
13. What is 123456 + 123
14. Given that the distance from vertex a of acute angle △ ABC to perpendicular h is equal to the radius of its circumcircle, then the degree of ∠ A is () A. 30°B. 45°C. 60°D. 75°
15. Given that the value of y = loga (3a-1) is always positive, then the value range of a is______ ．
16. In the RT triangle ABC, if ∠ C = 90 ° AB = 13 and the radius of the inscribed circle is 2, the perimeter of the triangle ABC is 0 Such as the title
17. In the parallelogram ABCD, if vector AB + vector ad = vector ab - vector ad, then there must be A vector ad = vector 0 B ABCD is a square C ABCD is a rectangle D vector AB = vector 0 or vector ad = vector 0
18. It is known that in △ ABC, BD bisects ∠ ABC, ed ‖ BC, EF ‖ AC, and it is proved that be = CF
19. Given vector a = (1,1 / 2), vector b = (0, - 1 / 2), vector C = vector a + k * vector B, vector D = vector a-vector B, the angle between vector C and vector D is π / 4, find the value of real number k in detail
20. As shown in the figure, in the triangle ABC, the angle ABC = 30 degrees, take BC and AC as sides, make equilateral △ BCD and equilateral △ ace, and connect be. To prove, AB square + BC square = be square