As shown in the figure, on the diagonal AC of square ABCD, cut CE = CD, make ef ⊥ AC, intersect ad at point F, and verify: AE = EF = FD

As shown in the figure, on the diagonal AC of square ABCD, cut CE = CD, make ef ⊥ AC, intersect ad at point F, and verify: AE = EF = FD

∵ ABCD is a square ∵ ade + ∵ CDE = 90 °
∵EF⊥AC ∴∠DEF+∠CED=90°
∫ CE = CD ∫ CDE = ∫ CED ∫ def = ∫ ade ∫ DEF is isosceles triangle ∫ EF = FD
∵ EF ⊥ AC and ∠ CAD = ∠ EAF = 45 °
∴AE=EF=FD

657 * 657-674 * 676 = how to calculate

675*675-674*676
=675*675-(675-1)*(675+1)
=675*675-675*675+1
=1

1. The service life of the front and rear tires of bicycles is different. Generally, for the same new tires, the service life of the front tires is 11000 km, and that of the rear tires is 9000 km. In order to scrap the front and rear tires purchased at the same time and use them for as long as possible, the front and rear tires should be replaced when they are used for a period of time
② The numbers are 1, 2, 3, 4 In 2007, all the 2007 colored lamps are on, and each lamp is controlled by a switch. If you press all the bulb switches whose number is multiple of 2 for the first time, press the bulb switch whose number is multiple of 3 for the second time, and press the bulb switch whose number is multiple of 5 for the third time, the last lamps that are still on are ()
A .1004 B.535 C.469 D.601
3. When recharging, the discount of China Mobile is to buy "100 for 30" and that of China Tietong is to buy 40 for 100 ". The call fee standard of these two companies is: 0.26 yuan per minute for China Mobile and 0.30 yuan per minute for China Tietong. Which company do you think is suitable for the actual call fee?
Answer: ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁

Question 1 4950
The second choice is C
Tietong cheap 0.41 per minute
I

A trapezoid becomes a parallelogram if its bottom is reduced by 6cm, and a trapezoid becomes a triangle if its top is reduced by 4cm
A trapezoid, if the bottom is reduced by 6cm, becomes a parallelogram
A trapezoid will become a triangle if its top and bottom are reduced by 4cm. The trapezoid used to be several centimeters

Because if you reduce the top and bottom by 4cm, it becomes a triangle
So the top and bottom are 4cm
Because if the lower sole is reduced by 6cm, it will become a parallelogram, which is the same as the upper sole
The bottom is 4 + 6 = 10 cm

How to calculate 56 * 7 + 77 * 4 skillfully

56*7+77*4=56*7+7*11*4=56*7+7*44=(56+44)*7=100*7=700

30 questions on Pythagorean theorem in mathematics of grade two
Don't talk nonsense

1. In RT △ ABC, if ∠ C = 90 ° and the lengths of the three sides are a, B and C respectively, then the following conclusions hold: A, 2abc2 D and 2Ab ≤ C2
2. Given that X and y are positive numbers and │ x2-4 + (y2-3) 2 = 0, if we make a right triangle with the length of X and y as the right side, then the area of the square with the hypotenuse of the right triangle as the side length is () a, 5b, 25C, 7d, 15d
3. If the length of one right side of a right triangle is 12 and the length of the other two sides is a natural number, there are () a, 4 B, 5 C, 6 D and 8 right triangles that meet the requirements
4. The following propositions: (1) if a, B and C are a group of Pythagorean numbers, then 4a, 4b and 4C are still Pythagorean numbers; (2) if two sides of a right triangle are 3 and 4, then the hypotenuse must be 5; (3) if three sides of a triangle are 12, 25 and 21, then the triangle must be a right triangle; (4) the three sides of an isosceles right triangle are a, B and C, (a > b = C), So A2 ∶ B2 ∶ C2 = 2 ∶ 1 ∶ 1, where ()
A、①② B、①③ C、①④ D、②④
5. If three sides a, B and C of △ ABC satisfy A2 + B2 + C2 + 338 = 10A + 24B + 26c, then △ is ()
A. Acute triangle B, obtuse triangle C, right triangle D, indeterminate
6. It is known that the waist length of an isosceles triangle is 10 and the height of one waist is 6. Then the area of a square with the bottom as the side length is ()
A. 40 b, 80 C, 40 or 360 D, 80 or 360
7. As shown in the figure, in RT △ ABC, ∠ C = 90 °, D is the point on AC, and Da = DB = 5, and the area of △ DAB is 10, then the length of DC is ()
A、4 B、3 C、5 D、4.5
8. As shown in the figure, a piece of right triangle paper, two right sides AC = 6 cm, BC = 8 cm. Now fold the right side AC along the straight line ad, so that it falls on the hypotenuse AB and coincides with AE, then CD is equal to ()
A、2㎝ B、3㎝ C、4㎝ D、5㎝
9. An ant climbs from point a to point B of a rectangular box with length and width of 3 and height of 8. What is the shortest route it takes_____________ .
10. On the calm surface of the lake, there is a red lotus, which is 1 meter above the surface of the water. When the wind blows, the red lotus is blown to one side, and the flowers reach the surface of the water. It is known that the horizontal distance of the red lotus is 2 meters. What is the depth of water here________ m.
1. As shown in the figure, a coastal open city a receives a typhoon warning. There is a typhoon center at 260km to the south of the city. It moves to D at the speed of 15km / h along the direction of BC. It is known that the distance between city a and BC is 100km. How long does it take for the typhoon center to move from point B to point d? If it is in a circular area 30km away from the typhoon center, it will be damaged by typhoon, Is it possible for tourists who are relaxing at d point to leave danger within a few hours after receiving the typhoon warning?
2. Arrays 3, 4, 5; 5, 12, 13; 7, 24, 25; 9, 40, 41 If the odd number n is a right side of a right triangle, the hypotenuse and the other right side are represented by an algebraic expression containing n. the next two groups of Pythagorean numbers are written
3. A square ladder is 25 meters long, as shown in the figure, leaning against a wall, and the bottom of the ladder is 7 meters away from the wall. (1) how high is the top of the ladder from the ground? (2) if the top of the ladder falls 4 meters, how many meters does the bottom of the ladder slide horizontally? (3) when the top of the ladder falls the same distance as the bottom of the ladder, how high is the top of the ladder from the ground?
4. As shown in the picture, a and B towns are on the same side of the river CD, and the distance to the river is AC = 10 km, BD = 30 km, and CD = 30 km. Now we need to build a water plant on the river to supply water to a and B towns. The cost of laying water pipes is 30000 yuan per kilometer. Please choose the location m of water plant on the river CD to save the cost of laying water pipes, and find out the total cost?

It is known that the parallelogram ABCD e is the midpoint of BC. Intercept AF = 1 / 2fd on ad, connect EF with AC, and calculate the value of Ag / AC from G
Similar with triangle
Ad parallel, BC.. CE not parallel

Ad and BC parallel
△AFG∽△CEG
AF/CE=AG/CG
AF=1/3AD
CE=1/2BC
BC=AD
AF/CE=1/3÷1/2=2/3
AG/CG=2/3
AG/AC=2/5

For a man-made earth satellite with mass m moving in a circular orbit, its distance to the earth is equal to the radius of the earth, and the acceleration of gravity on the ground is g
A. Satellite speed is root 2rg. Why wrong
B. The acceleration of the satellite is g / 2
c. The kinetic energy of the satellite is MRG / 4

On the ground, g = GM / R ^ 2, G -- gravitational constant, m -- mass of the earth, R -- high altitude radius of the earth, G '= GM / (2R) ^ 2 = (1 / 4) GM / R ^ 2 = g / 4, the satellite velocity is set as VV ^ 2 / (2R) = centripetal acceleration, a = g' = g / 4V = root sign (RG / 2). A wrong centripetal acceleration, a = mg '/ M = g' = g / 4. B wrong kinetic energy, EK = (1 / 2) MV ^ 2 = m [v ^ 2 / (2R)] * r

Calculation formula of surface area, volume and bottom area of cone (expressed in words)
It's Yuanzhu

Cone
Surface area s = n / 360 × π R × R + π R × R
Volume v = 1 / 3 π R × R × H
Bottom area s = π R × R
cylinder
Surface area s = π DH + 2 π R × R (π DH = 2 π RH)
Volume v = π R × R × H
Bottom area s = π R × R

The perimeter of a rectangular vegetable field is 200 meters, and the ratio of width to length is 3:2?

The length is 20 × 3 = 60 (m), the width is 20 × 2 = 40 (m), and the area is 40 × 60 = 2400 (M2). A: the area of this vegetable field is 2400 square meters