Calculate the result of 2cos ^ 2 22.5 degree ^It means square 1 / 2 "2 / 2" 3 / 2 "2 / 2" means root

Calculate the result of 2cos ^ 2 22.5 degree ^It means square 1 / 2 "2 / 2" 3 / 2 "2 / 2" means root

According to the half angle formula
cos^2(a/2)=(1+cosa)/2
therefore
2cos^2 22.5
=1-cos45°
=1-√2/2

1-2cos & # 178; 22.5 ° =?

1-2cos & # 178; 22.5 ° = - cos45 degree = negative half root sign two

1-2cos ^ 2 22.5 degrees and 1-2sin22.5 degrees
It's better to describe in words what formula this is. There is no square in the following topic

The first formula is: cos2x = 2cos ^ 2 X-1, then 1-2cos ^ 2 22.5 = - cos45sin22.5 can be obtained as follows: Formula: sin2x = 2sinx * cosx, let SiNx be t, then cosx = radical (1-T ^ 2), sin45 = 2T * radical (1-T ^ 2) = radical 2 / 2, t can be solved, and then it can be obtained by substituting 1-2sin22.5

Distinction between transverse direction and longitudinal direction of bridge
For example, which direction does the transverse direction and the longitudinal direction of the bridge refer to?
What is the direction of water flow of the bridge across the river? What is the direction of the route?

The transverse direction refers to the direction perpendicular to the bridge axis, and the longitudinal direction refers to the direction of the bridge axis
The direction of water flow is transverse to the bridge (if the water flow is perpendicular to the bridge), and the direction of route is along the bridge

Univariate linear equation (2710:50:8)
The walking speed of Xiaoming and Xiaogang is 4.5km/h and 3.5km/h respectively. They start from a and B at the same time. If they go in opposite directions, they will meet in 0.5 hours. If they go in the same direction, how many hours will it take Xiaoming to catch up with Xiaogang

The distance between a and B is as follows:
4.5 * 0.5 + 3.5 * 0.5 = 4km
When you travel in the same direction, if you have just walked x kilometers, you will have
X/3.5=(4+X)/4.5
X = 14 km
It takes Xiaoming 14 / 3.5 = 4 hours to catch up with Xiaogang

A. B is 135 kilometers away from the two places. There are two big and small cars driving from a to B at the same time. The big car is 4 hours and 30 minutes later than the car!
A. B is 135 km away from the two places. There are two big cars and two small cars driving from a to B at the same time. The big car is 4 hours and 30 minutes later than the small car. It is known that the speed ratio of the big car and the small car is 2:5. The speed of the two cars can be calculated

If the speed of a small car is 5x and that of a large car is 2x, the following results are obtained:
-135/5x+135/2x=5-0.5;
135*3=45x;
x=9;
So the speed of the car is 45 km / h and that of the cart is 18 km / h

As shown in the figure, C is the midpoint of line AB, and point D is the length of line AB, which is 3:2. Given CD = 8cm, find the length of ab
The process should be detailed

Let ad = 3x, DB = 2x, then AB = 5x, AC = AB / 2 = 5x / 2
CD=AD-AC=3X-5X/2=X/2 =8cm
X = 16cm
So AB = 5x = 5 * 16 = 80cm

The unit held the Spring Festival Flower party and bought four boxes of apples of the same weight. Each box took out 24 kg. As a result, the sum of the weight of the remaining apples in each box was just equal to the weight of the original box
I didn't think about how many kilos
How many kilos per case? Arithmetic and equation

24x4 (4-1) = 96 / 3 = 32kg / box

It is specified that a ⁃ B = 3A + 4b, 7 ⁃ x = 45 is known, and X is calculated

7※X=45
3*7+4*X=45
21+4X=45
4X=45-21
4X=24
X=6

240 kg of apples and pears are delivered to the fruit shop. The number of pears is one third less than that of apples. How many kg of pears are there?

Pear: Apple = (1-1 / 3): 1 = 2:3
Pear: 240 ÷ (2 + 3) x2 = 96 (kg)