2. (2010 Qingdao, Shandong Province) fold a rectangular piece of paper (rectangular ABCD) as shown in the figure, so that vertex B and point d coincide, crease

(2010 · Qingdao) folded a piece of rectangular paper (rectangular ABCD) as shown in the figure, so that the vertex B and point d coincide, and the crease is EF. If AB = 3cm, BC = 5cm, the area of the overlapping part △ DEF is ----- 3 --- CM & sup2;

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1. As shown in the figure, the rectangle ABCD with the length of 2 and the width of 1 rotates 90 ° clockwise with the top of the lower right corner as the center, and the coordinate of point a is_______ . turn 2 in turn The rectangle ABCD with length of 2 and width of 1 is rotated 90 ° clockwise with the vertex in the lower right corner as the center, and the coordinate of point a is_______ . rotate 2009 times in turn, then the coordinate of vertex A is________ .
2. As shown in the figure, the vertices a and B of rectangle ABCD are on the number axis, CD = 6, and the number corresponding to point a is - 1, then the number corresponding to point B is______ ．
3. As shown in the figure, the vertices a and B of rectangle ABCD are on the number axis, CD = 6, point E is the midpoint of AB, and the digit corresponding to point a is - 1, then the number corresponding to point E is
4. As shown in the figure, the vertices a and B of rectangle ABCD are on the number axis, CD = 6, and the number corresponding to point a is - 1, then the number corresponding to point B is______ ．
5. (2010 Hebei) the vertices a and B of rectangle ABCD are on the number axis, CD = 6, the number corresponding to point a is - 1, then the number corresponding to point B is -. I think it is 5 or - 7
6. As shown in the figure above, the coordinates of the four vertices of the quadrilateral ABCD are a (- 2,0), B (1,7) and C (5,5) As shown in the figure above, the coordinates of the four vertices of the quadrilateral ABCD are a (- 2,0), B (1,7), C (5,5) D (7,0) tries to find the area of this quadrilateral; As shown in the figure above, the coordinates of the four vertices of the quadrilateral ABCD are a (- 2,0), B (1,7), C (5,5) D (7,0) try to find the area of this quadrilateral;
7. There are two points a (1,7) and B (3,4) in the plane rectangular coordinate system. How to find a point C and D on the x-axis and y-axis to minimize the perimeter of the quadrilateral ABCD?
8. Given that point a (1,2) and point B (5,6) are of length 1, the segment CD moves on the x-axis. When the perimeter of quadrilateral ABCD is the smallest, the coordinate of point D is ()
9. The coordinates of each vertex of the quadrilateral ABCD are a (0.0), B (3.5), C (12.8) and D (15.0). Find the area of the quadrilateral
10. The vertex coordinates of the quadrilateral are a (- 1,4) B (2,2) C (4, - 1) d (- 2, - 2) respectively to find the area of the quadrilateral ABCD
11. If a circle passes through four vertices of a trapezoid ABCD, then the trapezoid is isosceles ∵AD∥BC, ∴∠A+∠B=180°, ∵∠A+∠C=180°, ∴∠B=∠C, The trapezoid ABCD is isosceles trapezoid; Why ∵ a + C = 180?
12. As shown in the figure, in the trapezoid ABCD, BC ‖ ad, ab = BC = CD = 2, ad = 4. The known point a coordinates are (- 2,0). Try to find the other three vertex coordinates of the trapezoid ABCD
13. Given that the coordinates of the three vertices of ladder ABCD are a (- 2,3), B (- 2,1), C (6,5), the equation of the straight line of the median line of the ladder is obtained
14. Let the vertex coordinates of ladder ABCD be a (- 1,2), B (3,4), D (2,1) and ab parallel to DC, the length of AB = 3 times the length of CD, then the coordinate of C is
15. In rectangular trapezoid ABCD. Ad = 7 & nbsp; & nbsp; ab = 2 & nbsp; & nbsp; DC = 3 & nbsp; & nbsp; P is a point on ad. the triangle with the vertex of P, a and B is similar to the triangle with the vertex of P, D and C. how many such points P have? Why?
16. Vertex a (- 2,2), B (- 1,4), C (4,5 +) of ladder ABCD, and AB / / DC, ab = 1 / 2dc, find the coordinates of vertex D Correction, C (4,5)
17. If the vertex a (- 1,2) B (3,4) d (2,1) of ladder ABCD and ab ‖ DC, ab = 2CD, then the coordinate of point C is?
18. Let the vertex coordinates of ladder ABCD be a (- 1,2), B (3,4), D (2,1), and ab is parallel to DC, ab = 2 DC, then the coordinates of point C are obtained AB = 2 DC with arrow (plane vector)
19. Given the three vertices a (1,2), B (3,4) and C (2,6) of ladder ABCD, find the point direction equation of the straight line where the median line of the ladder is located?
20. The ratio of the top to the bottom of a trapezoid is 3 / 5. The top is 1 meter shorter than the bottom, and the bottom is 25% higher. What is the area of this trapezoid?