As shown in the figure, ab ⊥ BC, BC ⊥ CD, BF and CE are rays, and ∠ 1 = 2, try to explain BF ⊥ CE

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• 1. There are four digits ABCD, and ABCD = (AB + CD) square, find all such four digits
• 2. In the trapezoid ABCD, ad ‖ BC, angle a = 90 °, ab = 7, ad = 2, BC = 3, whether there is a point P on the straight line AB, and find out the length of AP In the trapezoidal ABCD, ad ‖ BC, ∠ a = 90 °, ab = 7, ad = 2, BC = 3, ask whether there is a point P on the line AB, so that the triangle with P, a, D as the vertex is similar to the triangle with P, B, C as the vertex? If not, please explain the reason; if so, how many p points are there? And calculate the length of AP
• 3. The cross section of the reservoir dam is trapezoidal, the width of the dam crest is 5m, the slope ad = 6 √ 2m, the dam height is 6m, and the slope of the oblique wave bc i = 1: √ 3, Calculate the low width ab of the dam and the slope angle ∠ a of the slope ad
• 4. The cross section of a section of Zhanghe reservoir dam is isosceles trapezoid, the width of dam crest is 6m, the width of dam bottom is 126m, the slope gradient is 1: root 3, then the slope angle and height of the dam here are?
• 5. E. F is the key points of AD and BC on the sides of ABCD, and G and H are the midpoint of BD and AC fast
• 6. In trapezoidal ABCD, AD / / BC, median EF = 17cm, AC vertical BD, angle DBC = 30 degrees, calculate the length of diagonal AC
• 7. Tana * tanb is known in triangle ABC
• 8. Given the set a = {2,3, A2 + 1}, B = {A2 + a-4,2a + 1,1}, and a ∩ B = {2}, find the value of A
• 9. If the tolerance of arithmetic sequence an is - 1 and a1 + A2 + a3 +... + A2008 = 5022, then A2 + A4 + A6 +... + A2008 =?
• 10. For integers a, B, C, D, the symbol ∣ A / D - B / C ∣ denotes the operation AC – BD. given that 1 ∣ 1 / D - B / 4 ∣ 3, what is the value of B + D?
• 11. In the triangle ABC, 1. If ∠ C = 90, cosa = 12 / 13, find the value of SINB. 2. If ∠ a = 35, B = 65, try to compare the size of cosa and SINB If this triangle is an arbitrary acute triangle, can we judge the size of cosa + CoSb + COSC and Sina + SINB + sinc There is no graph
• 12. It is known that: as shown in the figure, in trapezoidal ABCD, ad ‖ BC, BC = DC, CF bisects ∠ BCD, DF ‖ AB, and the extension line of BF intersects DC at point E
• 13. It is known that the coordinates of three vertices of square ABCD are a (2,3) B (6,6) C (3,10), and the coordinates of point D can be obtained
• 14. Given the relative vertices a (0, - 1) and C (2,5) of square ABCD, the coordinates of vertices B and D are obtained
• 15. Given the line AB = 8cm, there is a point C on the line AB, and BC = 4cm, and the point m is the midpoint of the line AC, find the length of the line am
• 16. Given that point C is a point on line AB, ab = 12cm, AC: BC = 1:3, and point m is the midpoint of line BC, find the length of line am
• 17. Line AB = 40mm, draw line BC = 16mm on line AB, D is the midpoint of AC, and find the length of CD
• 18. In the isosceles triangle ABC, the vertical bisector of one waist AB intersects the other waist AC to F, the perpendicular foot is e, the perimeter of △ BFC is 20cm, ab = 12cm, Then the length of BC is___
• 19. It is known that point B is a point on the line AC, D is the midpoint of AC, e is the midpoint of AB, BC = 6. (1) draw a graph and find the length of de; (2) if (1) midpoint B is a point on the extension line of AC, other conditions remain unchanged, draw a graph and find the length of de
• 20. As shown in the figure, D is the midpoint of AC, DC = 2cm, BC = 1 / 2Ab, find the length of ab The picture shows: the middle part of a line segment (two endpoints: AC) is dB from left to right