After the circle is cut into an approximate rectangle, the perimeter is increased by 8 cm, and the perimeter and area of the circle are calculated

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• 1. If the sequence {xn} satisfies lgxn + 1 = 1 + lgxn and X1 + x2 + +If X100 = 100, LG (X101 + X102 +...) +x200）=（　　） A. 102B. 100C. 1000D. 101
• 2. A square steel plate, 9 / 8 meters in circumference, its area is () square decimeters
• 3. Let the population x ~ U (0, θ), x1, X2, ···, xn be a sample taken from the population, and x0 be the average number of samples (1) It is proved that θ 1 = 2x0, θ 2 = (n + 1) / N. x (n) is an unbiased estimate of θ (where x (n) = max {x1, X2, ···, xn}); (2) Which one of theta 1 and theta 2 is more effective (n ≥ 2)?
• 4. A bathroom is 1.8 meters long and 1.44 meters wide. Now we need to lay square tiles on the bathroom floor. How many centimeters is the maximum side length of square tiles?
• 5. Calculation of anomalous integral: ∫ (1,2) 1 / [x (LNX) ^ 2] DX= Where 1 is the lower limit and 2 is the upper limit,
• 6. On the round dining table with a diameter of 2 meters and a height of 1 meter, a square tablecloth is laid. The four corners of the tablecloth just touch the ground. The area of this tablecloth is () square meter.
• 7. What is the period of y = 2Sin Λ X-1? Odd function or even function?
• 8. There are several ways to make a big rectangle out of 60 squares of the same size
• 9. Rotate the line y = root 3x around the origin by 30 ° counterclockwise, and what is the inclination angle a = of the line
• 10. XY ^ 4 + YZ ^ 4 + ZX ^ 4-xz ^ 4-yx ^ 4-zy ^ 4 factorization I've seen three factors (X-Y) (Y-Z) (z-x) What's next?
• 11. Sine function y = SiNx, when the maximum value is y = 1, x = when the minimum value is y = - 1 Sine function y = SiNx, when the maximum value is y = 1, x = when the minimum value is y = - 1, X=
• 12. As shown in the figure, the perimeter of rectangle ABCD is 20cm. Take AB and ad as the sides, make square abef and square adgh outwards. If the sum of square abef and adgh area is 68cm2, then the area of rectangle ABCD is () A. 21cm2B. 16cm2C. 24cm2D. 9cm2
• 13. Some problems of physical atmospheric pressure in the second year of junior high school 1. Insert the straw into the bottle filled with water and suck the straw with your mouth. Can you suck the incoming water? Why? 2. Pour some hot water into the bottle, pour out the hot water, and then quickly close the cap. Why is the bottle shriveled? 3. After boiling water, the flask is fixed on the iron platform, and the peeled quail eggs are quickly put into the bottle mouth. You can see the quail eggs from the bottle mouth under the action of () thank you!
• 14. Cut off a rectangle 2cm wide from the square sheet, and the remaining area is 48cm2. Then the area of the original square sheet is () A. 9cm2B. 68cm2C. 8cm2D. 64cm2
• 15. A copper wire is 12.56 meters long. It is wound on a circular coil for 100 turns. What is the radius of the coil?
• 16. Know the area of a circle, how to find its perimeter, diameter, radius
• 17. A mathematics application problem urgent I! Fang Hua's family has a 40 cm long and 25 cm wide glass fish tank with a water depth of 20 cm. One day, Fang Hua accidentally dropped a 10 cm square iron block into the tank. How many cm will the water surface rise? But also the solution ideas and the meaning of each formula! It's up to, remember, it doesn't seem to be up to how many centimeters!
• 18. As shown in the figure, it is known that in the quadrilateral ABCD, ad ‖ BC, ad > BC, ab = DC, EA = ed, EB and EC intersect ad at points F and g respectively to prove that the quadrilateral fbgc is isosceles trapezoid
• 19. If A-B = B-A and a = 4, B = 3, find the value of a + B
• 20. CD / / EF / / AB, CD = 2, ab = 4. EF bisects the area of trapezoid ABCD and finds the length of EF CD / / EF / / AB, CD = 2, ab = 4. EF bisects the area of the trapezoid ABCD to find the length of EF (requires a problem-solving process)