Use a scale and a compass to make a line so that its length is 3 cm

Use a scale and a compass to make a line so that its length is 3 cm

As shown in the figure, for your reference
If the point a on the number axis represents the negative root sign 3, then the point 3 units of length away from a represents the number?
3 minus root 3
The number represented by three points of unit length away from the root sign 3 on the number axis is as follows:
3+√3,
-3+√3
The distance from the number axis to - radical 5 is equal to 2 points of unit length, which means the number is____________
The distance from the number axis to - radical 5 is equal to 2 points of unit length, which means the number is - radical 5 plus 2 and - radical 5 minus 2
The distance from the number axis to the - radical 5 is equal to the number x represented by two points of unit length
|X﹣﹙﹣√5﹚|=2
∴X=±2﹢√5
X1=√5﹢2
X2=√5﹣2
It is known that 2cos ^ 2A + 3cosasina-3sin ^ 2A = 1. Find 2sina-3cosa / 4sina-9cosa
It is known that 2cos ^ 2A + 3cosasina-3sin ^ 2A = 1
2cos^2a+3cosasina-3sin^2a
=(2cos ^ 2A + 3cosasina-3sin ^ 2a) / (COS ^ 2A + sin ^ 2a) numerator and denominator divided by cos ^ 2A at the same time
=(2+3tana-3tan^2a)/(1+tan^2a)
=1
SO 2 + 3tana-3tan ^ 2A = 1 + Tan ^ 2A
4tan^2a-3tana-1=0
(4tana+1)(tana-1)=0
Tana = - 1 / 4 or Tana = 1
2sina-3cosa/4sina-9cosa
=(2tana-3)/(4tana-9)
(1) tana=-1/4
(2tana-3)/(4tana-9)=(-1/2-3)/(-1-9)=7/20
(2) tana=1
(2tana-3)/(4tana-9)=(2-3)/(4-9)=1/5
2cos^2a+3cosasina-3sin^2a=1
2cos^2a+3cosasina-3sin^2a-sin^2a-cos^2a=0
cos^2a+3cosasina-4sin2a=0
(cosa+sina)(cosa-4sina)=0
Cosa = - Sina or cosa = 4sina
Tana = - 1 or Tana = 1 / 4
(2sina-3cosa)/(4sina-9cosa)
=(2tana-3)/(4tana-9)
When Tana = - 1, the original formula is 5 / 13
When Tana = 1 / 4, the original formula is 5 / 16
How to convert wind energy into electricity and how to store electricity
First, the wind drives the blades to rotate, and the wind energy is converted into mechanical energy
Then through the gear conversion, drive the internal impeller rotation, mechanical energy transmission
The impeller is located in a magnetic field. After rotating, the mechanical energy is converted into electric energy
There are many ways to store electricity. It depends on the situation
In general, it is directly connected to the power grid
Some seaside power stations use extra power to pump water to high places, and use hydroelectric generating units to generate electricity when power is insufficient
Some power stations on the plain will use compressed air. Then they will use compressed air to generate electricity
This is only a part of the examples. I will not list the others one by one
The wind energy is first converted into kinetic energy, then into electric energy through the generator
A plus one is two. How much is a
a=2-1=1
Use the method of number axis to deduce the operation rules of addition, subtraction, multiplication, division and power of rational numbers
Yes, in fact, it's the combination of ruler and graph, number and shape
If Tana = 4, then sinacosa-2cos ^ 2A =
sinacosa-2cos^2a
=(1/2)sin2a-(cos2a+1)
Using the universal formula: Tana = 4, sin2a = 8 / 17, cos2a = - 15 / 17
Then the original formula is 2 / 17
How can solar energy and wind energy be converted into electricity together?
The working principle of their electric energy conversion technology is different. Solar energy is generated by light conversion, while wind energy is generated by the rotation of the fan blades to drive the generator. However, both solar energy and wind energy are converted into electric energy together