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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
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- 1. 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?
- 2. 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
- 3. 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
- 4. 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
- 5. 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,
- 6. 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?
- 7. 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)
- 8. The sides of the two squares are 4cm and 8cm respectively, and the area of the shadow is___ square centimetre There is no picture
- 9. Use a square whose side length is a centimeter to make a square
- 10. 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
- 11. 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___ ．
- 12. In quadrilateral ABCD,
- 13. 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?
- 14. 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？ 、
- 15. If the volume of the cone is equal to that of the ball, and the radius of the bottom of the cone is twice that of the ball, then the ratio of the side area of the cone to the surface area of the ball is 0
- 16. It is known that the height of a cone is 6cm and the length of generatrix is 10cm. It is necessary to calculate the volume of the inscribed sphere and the surface area of the circumscribed sphere
- 17. The axial section of a cone is an equilateral triangle with a side length of 2 root sign 3. The volume of the cone is equal to
- 18. The length of the generatrix of the cone is 4, and the area of the cross-section triangle passing through the vertex is 4 root sign 3. Find the vertex angle of the cross-section triangle (2), the height of the cone is l, and the bottom radius is root sign 3 Find the maximum cross-sectional area of a cone vertex
- 19. If the height of the cone is 2 and the radius of the bottom is 2 root sign 3, the maximum cross-sectional area of the cone will be obtained
- 20. If the side area of a cone is 8 π square centimeter and its axis section is an equilateral triangle, the area of the axis section is () a 8 root sign 3 cm & # 178; B 4 root C 8 is 3 π CM & # 178; D 4 is 3 π CM & # 178;