Is there a real number a such that sin a + cos a = 3 / 2

Is there a real number a such that sin a + cos a = 3 / 2

Sin a + cos a = radical 2 × sin (a + 45 °) = 3 / 2 sin (a + 45) = triple radical 2 / 4, because if triple radical 2 / 4 > 1, there is no real number to make the equation hold

Solve binary linear equations
Given the system of equations {ax + 5Y = 15, ① 4x-by = - 2, ② a gets the solution of the system of equations {x = - 3, y = - 1 because of reading a wrong equation. B gets the solution of the system of equations {x = 5, y = 4 because of reading B wrong equation

First of all, because a is wrong about a, but B is not wrong, so the value of B is right. Let's find out B first, substitute x = - 3, y = - 1 into the equation group, and get b = 10. Similarly, B is wrong about B, and the value of a is right. Find out a, and then substitute x = 5, y = 4 into the equation group, and get a = - 1, so the correct a and B are both

Derivative of piecewise function
How to use the definition of derivative to find the derivative of piecewise function at the dividing point?
Do you have both formulas? (I'm just learning derivative.)

Wow, this should be done with the limits of University
If the limits of the two sides are not equal, then they are not differentiable. Only when they are equal can they be differentiable

If the lengths of the three sides of the triangle ABC are a, B, C respectively, and satisfy the condition a + B + C + 338 = 10A + 24B + 26c, try to judge the shape of the triangle ABC
And prove why. In a hurry

a²+b²+c²+338=10a+24b+26c
(a²-10a+25)+(b²-24b+144)+(c²-26c+169)=0
(a-5)²+(b-12)²+(c-13)²=0
So a = 5, B = 12, C = 13
Can get
c²=a²+b²
So triangle ABC is a right triangle and angle c is a right angle

I did a time experiment! It proved the hypothesis of Einstein's special theory of relativity!
Is it possible to reverse the flow of time? Is it possible for us to go back to a certain time in the past? Is it possible that as long as we are infinitely close to the speed of light, strange changes will occur in time and space? In order to verify this problem, I did an amazing time experiment in April this year, which was supported by the local culture bureau and the Transportation Bureau of course! The experiment is like this: with the help of the Transportation Bureau, In addition to a driver's car, the observer and myself are planning to carry out experiments on the highway! I also took three watches, which were identified by experts as working normally! So I adjusted the time for the same number of seconds, one of which was held by the witness, the other two were safely put in the car, and locked them up, I also prepared a high-definition pixel digital camera, which was firmly placed in the front of the car. The lens started the digital camera to shoot everything in front of the car. Then the driver of the racing car arranged by the witness was responsible for driving. He put on his seat belt, and finally sprinted forward from slow to fast. In fact, in theory, he would drive at full speed at the end! I have witnesses, Half an hour later, the driver got out of the car and waited for us to get to the destination. The first thing I asked him was how he felt. He said, "I drove at full speed, and the engine and exhaust pipe were still hot and smoking. It almost exploded! But it was really exciting! It was like racing.", I gave the key to the witness, who opened the lock and took out the watch. The witness looked at it carefully, rubbed his eyes again, and suddenly said, "am I dazzled? The time of the two watches in the car is a little slower in seconds than that of the one on me. Although this is a microsecond time difference, it is enough to prove that, When an object moves infinitely close to the speed of light, it can slow down its own time! But the outside world remains normal! What's more shocking is that when we watch the 30 minute video taken by the digital camera, we find that when the car is driving slowly, all the scenes outside are the same as the reality. When the car is gradually speeding up, it reaches full speed all the time, and strange phenomena occur, At the beginning of the lens, there was a blue circle wave in the middle, and at the end, there was a red circle wave at the edge of the lens. When the red circle wave appeared, the houses, woods, sky and roads outside were gradually compressed into a curved shape in the middle, became a circle, and then gradually became smaller, The outer space will be compressed! It can be boldly imagined that if the speed of light is reached, or even faster than the speed of light, then the outer scene will not only be compressed into a circular shape, but will rush into the space where it appears, that is, tear the space and break into the unknown unknown space. It may be a few days ago now or in ancient times. Therefore, this experiment proves that it is possible to reverse the flow of time, One of the ways to choose superluminal speed is not ideal, which is considered stupid. In today's world, no object can move faster than the speed of light, and it is not allowed to move faster than the speed of light. Because the speed of light is the fastest. Another way is wormholes, which is relatively ideal. I am sure that there are wormholes in the universe, and they will not be explored at will, Even if we find it, we can't get through it. It's so attractive that we can't even escape light, let alone human beings. Of course, we can use artificial wormholes. The current level of science and technology has not reached that level. Here, Einstein's special theory of relativity can only say that time reversal is OK in theory, but in reality we are not allowed to go back to the past!
You can make a point

He didn't say that time will flow backward, Einstein's relativity formula: T = 1 / √ [1 - (V ^ 2 / C ^ 2)], when an object exceeds the speed of light, time will be meaningless. (it's an imaginary number, not a negative number!)
And no object can exceed the speed of light. The greater the speed is, the greater the mass will be. Einstein's famous equation of equivalence between energy and mass is that the energy of an object due to its motion will be transferred to its mass. The mass of an object with 10% speed of light is 100.5% of the original, but the mass of an object with 90% speed of light is more than twice of the original. When the object reaches the speed of light, the mass will be infinite, It's impossible to accelerate it to the speed of light
When the European hadron pair was installed, it didn't happen to accelerate the particles to near the speed of light. As the landlord said, it didn't even reach tens of thousands of times the speed of light. These phenomena can't happen

Calculation: (3x + 4) (3x-4) - (2x + 3) (2x-3)

（3x+4)(3x-4)-(2x+3)(2x-3)
=(9x²-16)-(4x²-9)
=9x²-16-4x²+9
=5x²-7

The circumference of a rectangle is 26cm. If the length of the rectangle is reduced by 1cm and the width is increased by 2cm, it can become a square,
What is the length and width of the original rectangle,

Suppose the length is x cm and the width is 26 △ 2-x cm
x-1=26÷2-x+2
x-1=15-x
2x=16
x=8
Width = 26 △ 2-8 = 5cm
A: 8 cm long and 5 cm wide

What is the relationship between rad / min and R / S? How to change them into angular velocity

The former is radians per minute, and the latter is revolutions per second, which are actually units of angular velocity
Every revolution is equivalent to 2 π radians, 60 seconds per minute, R / s times 120 π, which is rad / min

The maximum value of the function y = x4-4x + 3 in the interval [- 2,3] is______ ．

∵ y = x4-4x + 3, ∵ y '= 4x3-4, when y' = 4x3-4 ≥ 0, X ≥ 1, the function y = x4-4x + 3 monotonically increases ∵ on [1,3], when x = 3, the function takes the maximum value 72, when y '= 4x3-4 < 0, x < 1, the function y = x4-4x + 3 monotonically decreases ∵ on [- 2,1], when x = - 2, the function takes the maximum value 27

Figure 1 is a square cardboard with side length of 30. After cutting off the shadow part, fold it into a cuboid box as shown in Figure 2. Given that the width of the cuboid is twice the height, what is its volume?

The height of the cuboid is xcm, and then its width is 30 − 2x2 = 15-x. according to the Title Meaning: 15-x = 2x, the solution is: x = 5, so the cuboid's width is 10, and its length is 20cm, then the cuboid's volume is 5 × 10 × 20 = 1000cm3