Finding the knowledge points of the first chapter of mathematics triangle

Finding the knowledge points of the first chapter of mathematics triangle

Junior high school mathematics theorem formula induction 1 Deduction 1 bisector of the vertex angle of isosceles triangle bisectors the bottom edge and is perpendicular to the bottom edge 2 bisector of the vertex angle of isosceles triangle, the middle line on the bottom edge and the height coincide with each other 3 Determination theorem of isosceles triangle if a triangle has two equal angles, Then the sides of the two angles are equal (equal angles to equal sides) 4 corollary 2 an isosceles triangle with an angle equal to 60 ° is an equilateral triangle 5 in a right triangle, If an acute angle is equal to 30 degrees, then the right side it faces is equal to half of the hypotenuse. 6. The middle line on the hypotenuse of a right triangle is equal to half of the hypotenuse. 7. Theorem the distance between the point on the vertical bisector of a line segment and the two ends of the line segment is equal. 8. Inverse theorem and the distance between the two ends of a line segment is equal, On the vertical bisector of this line segment 9, the vertical bisector of this line segment can be regarded as a set of all points with the same distance from the two ends of the line segment 10 theorem 1 two figures symmetrical about a line are congruent 11 theorem 2 if two figures are symmetrical about a line, then the axis of symmetry is the vertical bisector of the line corresponding to the point 12 Theorem 3 two figures are symmetrical about a line, If their corresponding line segments or extension lines intersect, then the intersection point is on the axis of symmetry 13 inverse theorem if the line of the corresponding points of two figures is vertically bisected by the same line, then the two figures are symmetrical about the line 14 Pythagorean theorem the sum of the squares of the two right angles a and B of a right triangle is equal to the square of the hypotenuse C, That is, a + B = C 15 inverse theorem of Pythagorean theorem. If the lengths of three sides of a triangle a, B and C are related to a + B = C, then the triangle is a right triangle

Scientific knowledge of grade one in junior high school: where is the indoor unit of air conditioner installed? It has something to do with the flow of air!

Should be installed in high places, cold air down, and indoor air convection, improve indoor temperature

Scientific knowledge and ability training in the first year of junior high school?
1. Why is there a birthday annular eclipse, but not a monthly annular eclipse?
2. Xiao Fang said she saw the lunar eclipse during the Spring Festival, while Xiao Li said she saw the solar eclipse during the Spring Festival. Which one of them is credible? Why?
3. Why fewer people can see total eclipse than partial eclipse?

1. Annular eclipse this is because the moon is between the sun and the earth, but it is far away from the earth, so it can not completely cover the sun. No annular eclipse is because the earth blocks the light from the sun to the moon. The earth is bigger than the moon, so it can completely cover the moon, so it will not happen. 2

Scientific knowledge of environmental protection

Classification and sources of air pollution
Air pollution refers to the phenomenon that some substances are involved in the atmosphere due to human activities or natural processes, showing enough concentration and reaching enough time, and thus endangering human comfort, health and welfare, or endangering the environment. The so-called human activities include not only production activities, but also living activities, such as cooking, heating, transportation, etc, Generally speaking, due to the self purification of the natural environment, the air pollution caused by natural processes will be automatically eliminated after a certain period of time. Therefore, the air pollution is mainly caused by human activities
According to the scope of pollution, air pollution can be roughly divided into four categories
① The air pollution limited to people, such as being directly affected by the exhaust from some chimneys;
② Involving air pollution in an area, such as air pollution in the industrial area and its vicinity or the whole city;
③ It involves wide area pollution in a wider area than a city;
④ The global pollution that must be considered from the global scope, such as the increasing of dust and carbon dioxide in the atmosphere, has become the global pollution and has attracted the attention of all countries in the world
Air pollution sources refer to places, equipment and devices that discharge harmful substances or produce harmful effects on the atmospheric environment. According to the sources of pollutants, they can be divided into natural pollution sources and man-made pollution sources
1. Natural pollution sources
The place where some natural phenomena discharge harmful substances or cause harmful effects to the environment is a very important source of air pollutants. Although compared with man-made pollution sources, the types of air pollutants produced by natural phenomena are less and the concentration is lower, which may cause serious impact in some local areas, from a global point of view, natural sources are still very important, The main natural sources of air pollutants are as follows:
1) Volcanic eruption: emission of SO2, H2S, CO2, Co, HF and volcanic ash
2) Forest fire: emission of CO, CO 2, so 2, no 2, HC, etc
3) Natural dust: wind sand, soil dust, etc
4) Forest plant release: mainly terpene hydrocarbons
5) Sea spray: particles are mainly sulfate and sulfite
In some cases, natural sources are more important than man-made sources. Some people have estimated the global emissions of sulfur oxides and nitrogen oxides. They think that 93% of the global emissions of nitrogen oxides and 60% of the global emissions of sulfur oxides come from natural sources
2. Anthropogenic pollution sources
Human production and living activities are the main sources of air pollution. Generally speaking, air pollution sources refer to the sources of pollutants transported to the atmosphere by human activities
Fuel combustion industry production process transportation agricultural activities
Fuel combustion: the combustion process of coal, oil, natural gas and other fuels is an important source of pollutants to the atmosphere. Coal is the main industrial and civil fuel, its main component is carbon, and contains hydrogen, oxygen, nitrogen, sulfur and metal compounds, In the combustion process, carbon monoxide, carbon dioxide, sulfur dioxide, nitrogen oxides, organic compounds and smoke and other harmful substances will be formed
Thermal power plants, iron and steel plants, coking plants, petrochemical plants, factories with large boilers and industrial and mining enterprises with the largest amount of coal consumption have different degrees of air pollution according to the nature and scale of industrial enterprises
Household stove exhaust is a kind of air pollution source with large emission, wide distribution, low emission height and harm
Industrial production process emissions: industrial production process emissions into the atmosphere of a large number of pollutants, is an important source of air pollution in cities or industrial areas
There are many factories that discharge waste gas in the process of industrial production, Petrochemical enterprises emit sulfur dioxide, hydrogen sulfide, carbon dioxide and nitrogen oxides; non-ferrous metal smelting industry emits sulfur dioxide, nitrogen oxides and dust containing heavy metals; phosphate fertilizer plant emits fluoride; acid and alkali chemical industry emits sulfur dioxide, nitrogen oxides, hydrogen chloride and various acidic gases; iron and steel industry emits sulfur dioxide, nitrogen oxides and dust in the process of ironmaking, steelmaking and coking Dust, sulfur oxides, cyanide, carbon monoxide, hydrogen sulfide, phenol, benzene, hydrocarbons, etc. in short, the composition of pollutants emitted from industrial production process is closely related to the nature of industrial enterprises
Emissions from transportation: automobile exhaust has become the main source of air pollution. The development of motor vehicles is very fast. The number of motor vehicles in the world was 70 million in 1950, and it increased to 710 million in 1996. The main pollutants emitted by gasoline vehicles are co, NOx, HC and lead (if leaded gasoline is used); the main pollutants emitted by diesel vehicles are NOx, PM (fine particulate matter), HC and HC, Compared with developed countries, China's motor vehicle emissions are quite amazing. Take Tokyo, Japan as an example, in the 1990s, Tokyo had 4 million motor vehicles, while the emissions of CO and NOx were basically stable at about 100000 t and 50000 T, while Beijing only had 1 million motor vehicles in 1995, while the emissions of CO and NOx were as high as 972000 T and 98000 t
Emission from agricultural activities: the use of pesticides and chemical fertilizers plays an important role in improving agricultural production, but it also brings adverse effects on the environment, which makes agricultural activities using pesticides and chemical fertilizers become an important source of air pollution
When pesticides are applied in the field, some of them will escape into the atmosphere in the form of dust and other particles, and those remaining on or adhering to the surface of crops can still volatilize into the atmosphere. The pesticides entering the atmosphere can be absorbed by the suspended particles and transported with the air to various places, causing pesticide pollution in the atmosphere
For example, nitrogen oxides will be released into the atmosphere after a series of changes of nitrogen fertilizer in the soil; nitrogen can form nitrogen (N2) and nitrous oxide (N2O) under denitrification, which can be released into the air. Nitrous oxide is insoluble in water and can be transported to the stratosphere and interact with ozone, The ozone layer is destroyed
In addition, in order to analyze the movement of pollutants in the atmosphere, according to the characteristics of pollution sources, it can be divided into fixed pollution sources and mobile pollution sources. Fixed pollution sources refer to the pollutants discharged from fixed places, such as various industrial production and domestic stove emission sources, whose position is fixed; mobile sources refer to various means of transportation, Such as cars, ships, airplanes and so on, are all kinds of harmful pollutants emitted to the surrounding atmospheric environment during sports. According to the spatial distribution of pollutants, they can be divided into point pollution sources, that is, pollutants that are concentrated at a point or can be regarded as a point in a small area; non-point pollution sources, that is, pollutants that are discharged in a large area

The second year or above of science knowledge
If the displacement of a ship is 5000 tons and the maximum carrying capacity is 3500 tons, how much buoyancy does the ship receive when it is fully loaded? If the ship only carries 2000 tons, how much buoyancy does it receive? (g = 10 N / kg)
The water density is 1.0 × 1000kg / m3

Students! We need to find out what displacement is, and then calculate it! Alas! Full load buoyancy = displacement fman = m full row g = 5000000 * 10 = 50000000 Newton ship's weight G1 = fman - M cargo g = 50000000-35000000 = 15000000 Newton. If the ship only carries 2000 tons of cargo, it will be affected by buoyancy fman = G1 + m cargo g = 150

Mathematics, scientific knowledge, please help answer a few questions, please bring the process
(1) Find the largest integer smaller than root 7 and the smallest integer larger than root 7
(2) Find the largest integer smaller than 2000 radical 8 and the smallest integer larger than 2000 radical 8
(3) Boss Wang, who is in the clothing business, runs two stores, a and B. each store can sell 30 pieces of a and B styles at the same time. For each piece of a and B styles sold, the gross profit of store a is 30 yuan and 40 yuan respectively, and that of store B is 27 yuan and 36 yuan respectively, How to allocate 30 pieces of clothing to each store, so that under the premise of ensuring that the gross profit of store B is not less than 950 yuan, boss Wang gets the largest gross profit? What is the largest gross profit?
(4) A shop comes in a batch of woolen sweaters at the price of 50 yuan / piece. The preliminary market survey shows that if it is sold at the price of 60 yuan / piece, 100 pieces can be sold every week. On this basis, if the sales price is increased by 5 yuan per piece, the weekly sales volume will be reduced by 4 pieces. Suppose that the shop sets the sales price as X Yuan / piece (x is greater than or equal to 60)
What is the weekly gross profit of the store? (gross profit = sales revenue purchase cost)

(1) The largest integer smaller than root 7 is 2, and the smallest integer larger than root 7 is 3
(2) The maximum should be 5656