Who knows the area formula of a circle, the arc length formula of a circle, and the sector area formula

The area of the circle s = π R & sup2; (R is the radius of the circle)
The arc length of a circle L = | α | * r (| α | is the center angle of a circle in radians, R is the radius of a circle)
Sector area s = 1 / 2 * L * r (L is the arc length of sector and R is the radius of circle)
Or = 1 / 2 * | α | * r & sup2; (| α | is the center angle of the arc system, R is the radius of the circle)

RELATED INFORMATIONS

1. The original price of a commodity is 200 yuan. After the price is reduced by 5%, the price is increased by 5%, and the current price is increased by 5%___ Yuan
2. The current price of a coat is 200 yuan, which is 50 yuan lower than the original price. How much lower?
3. A kind of TV set, the original price is 2200 yuan, the current price is 200 yuan, how much is the price reduction
4. For a commodity, the original price is 1000 yuan, but now the price is reduced by 200 yuan. How much has the price been reduced
5. 2. The original price of a commodity is 52 yuan, and the current price is 39 yuan. How much is the price reduction? 3. The electricity consumption of the school this month is 900 degrees, which is 10% less than that of last month 4. When a typist types a manuscript, the ratio of the number of pages typed on the first day to the total number is 1:10. If he type six more pages, he can finish 15% of the manuscript. How many pages does the manuscript have For the formula, just answer the fourth question
6. The original price of a commodity is 52 yuan, and the current price is 39 yuan. The price has been reduced______ %．
7. A commodity price is raised by 20% and then reduced by 20%. The current price is compared with the original price A. The current price is the same as the original price B. the current price is lower than the original price C. The current price is higher than the original price D. It's not easy to compare
8. The goods are sold at a 10% discount, indicating that the current price is ()% lower than the original price
9. A 20% discount on a product means that the current price is ()% of the original price and ()% cheaper than the original price
10. A 10% discount on a product means that the original price is one tenth cheaper than the current price. Why?
11. Given the line L: y = 3x + 3, find: (1) the equation of the line x-y-2 with respect to the line L symmetric, (2) the equation of the line L with respect to the line m (3,2) symmetric
12. P is a point on the ellipse x ^ 2 / 25 + y ^ 2 / 16 = 1, F1 and F2 are the focus. If ∠ f1pf2 = 30 °, then the area of △ f1pf2 is Why let Pf1 = m, PF2 = 10-m, and then use Pythagorean theorem to calculate that there is no solution Wrong number for ∠ f1pf2 = 90 °
13. How to calculate the area of irregular figure?
14. When | x | is less than or equal to 1, find the minimum value of square x-2ax + a of quadratic function y = X When | x | is less than or equal to 1, find the minimum value of square x-2ax + a of quadratic function y = X
15. It is known that the quadratic equation AX2 + BX + C = 0 with respect to X. when the coefficients a, B and C satisfy a-2b + 4C = 0, there is a root which can be determined. The root is: - (excluding a, B and C)
16. The right focus of hyperbola C x ^ 2 / A ^ 2-y ^ 2 / b ^ 2 = 1 (a greater than 0, b greater than 0) is f passing F, and the intersection C of straight line with slope root 3 is at two points a and B If the vector AF = 4, find the eccentricity of C with the vector FB
17. A-B + C = 2 (1) a + B + C = 1 (2) 4A + 2B + C = 3 (3) how to solve the ternary linear equations?
18. Given that real numbers x, y, Z satisfy X-Y = 8, XY + Z2 = - 16, then x + y + Z=______ ．
19. The analytic region of the following function f (x) is pointed out and its derivative is obtained （1）Z^3+2iZ ;
20. It is known that the image of quadratic function y = x2 + BX + C passes through two points a (0,1), B (2, - 1). (1) find the value of B and C; (2) try to judge whether the point P (- 1,2) is on the parabola