If point E is the midpoint of BC and point F is the midpoint of AD, then the angle between AB and EF is 45?

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• 1. Given the line I: y = 3x + 3, the equation of the line x-y-2 = 0 with respect to the l-symmetric line is obtained From x-y-2 = 0 and 3x-y + 3 = 0, x = - 5 / 2, y = - 9 / 2 Then three straight lines intersect at the point: (- 5 / 2, - 9 / 2) Let the linear equation be y + 9 / 2 = K (x + 5 / 2) The angle from the straight line x-y-2 = 0 to the straight line 3x-y + 3 = 0 is equal to the angle from the straight line 3x-y + 3 = 0 to the straight line (3-1)/(1+3),=(K-3)/(1+3k) So, k = - 7 So the linear equation is: 7x + y + 22 = 0 Why is the angle from the straight line x-y-2 = 0 to the straight line 3x-y + 3 = 0 equal to the angle from the straight line 3x-y + 3 = 0 to the straight line (3-1)/(1+3),=(K-3)/(1+3k)
• 2. The sides of the two squares are 4cm and 8cm respectively, and the area of the shadow is___ square centimetre There is no picture
• 3. Use a square whose side length is a centimeter to make a square
• 4. Given that the generatrix length of the cone is 30, and the center angle of the fan-shaped circle is 120 ° after the side expansion, the bottom radius of the cone is 0______ Detailed explanation
• 5. The diameter of circle a is 10 cm, which is 50% of the diameter of circle B. what is the circumference of circle B Come on, come on
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• 8. The circumference of the rectangle is 24 cm, the ratio of length to width is 2:1, and the area of the rectangle is 2______ ．
• 9. Find the range of the real number m so that the two X1 and X2 of the equation x2-2 (m-1) x + 3m-6 = 0 satisfy the following conditions: X1 > 2, X2 > 2 Find the range of real number m, so that the two X1 and X2 of equation x2-2 (m-1) x + 3m-6 = 0 satisfy the following conditions: X1 > 2, X2 > 2, but the answer given by the teacher is - 1 < m < 2
• 10. 1. How to add or subtract 2, 3, 4, 5, 6, 7 to make it equal to 11
• 11. Given rectangle ABCD, where AB = 5, BC = 8, AE ‖ BD, trapezoid ABDE, find the area of triangle BDE It's a rectangle ABCD with a triangle ade on it,
• 12. Fold one side of rectangle ABCD along de so that point C falls at point F on the edge of ab. if ad is equal to 8 and the area of triangle is 60, calculate the area of triangle Dec
• 13. As shown in the figure, in the rectangular ABCD, AC is a diagonal, rotate ABCD clockwise 90 ° around point B to gbef position, h is the midpoint of eg, if AB = 6, BC = 8, then the length of segment ch is () A. 25B. 21C. 210D. 41
• 14. As shown in the figure, the rectangle ABCD rotates 90 ° clockwise around point a to the position of rectangle ab1c1d1. Ad = 10, calculate the area swept by edge BC
• 15. As shown in the figure, fold a rectangular piece of paper ABCD along AF to make point B fall at B ′. If ∠ ADB = 20 °, then how many degrees should ∠ BAF be to make ab ′‖ BD?
• 16. As shown in the figure, the rectangular piece of paper ABCD, ∠ ADB = 30 ° is folded along the diagonal BD (so that △ abd and triangle EBD fall in the same plane), when Ao = 2 cm, the length of ad is calculated
• 17. As shown in the figure, rectangular paper ABCD, ab = 2, ∠ ADB = 30 ° is folded along the diagonal BD (so that △ abd and △ EBD fall in the same plane), then the distance between a and E is___ ．
• 18. In quadrilateral ABCD,
• 19. If the radius of the base area of the cone is √ 3 and the surface area of the inscribed sphere is 4 π, then the side area of the cone is?
• 20. If the height of the circumscribed cone of a sphere is three times the radius of the sphere, what is the ratio of the side area of the cone to the surface area of the sphere? It's a process. There is also a question: a cylindrical cylinder with a bottom radius of R is filled with an appropriate amount of water. If a solid iron ball with a radius of R is put in, the height of the water surface will just rise R. R/r？ 、