Mathematical formula is an expression method that people find some connection between things in nature and express it in some way. It represents the equal or unequal relationship between the quantities of different things in nature, accurately reflects the internal and external relations of things, and is the basis for us to reach another thing from one thing, so as to better understand the essence and connotation of things.
Basic formula common sense
The circumference of a rectangle = (length+width) ×2 = 2(a+b) = (a+b)×2.
Trapezoidal area = (upper bottom+lower bottom) × height ÷2 S=(a+b)h÷2.
Area of triangle = base × height ÷2 S=ah÷2.
Area of rectangle = length× width S = ab.
Extended data
The test of determining the adaptability of components, equipment or other products to a certain altitude (low pressure) environment during storage, transportation and use, putting the sample into a test box (room), and then reducing the air pressure in the box (room) to the value specified by relevant standards and maintaining the specified duration is called altitude test (also called low pressure test). If the height below a certain water level is -500m, the environmental adaptability test is called positive pressure test.
In the international system of units, the standard unit of length is "meter", which is represented by the symbol "m". 1960 The 1st International Metrology Conference: "The length of the meter is equal to 1650763.73 times of the radiation wavelength between the 2P 10 and 5d 1 levels of krypton -86 atoms in vacuum".
From 1983, the length of meter is defined as "the distance that light travels in vacuum in 1/299 792 458 seconds". The unit of length adopted in China is consistent with the international system of units, that is, "meter" is the legal unit of length measurement in China.
Baidu Encyclopedia-Mathematical Formula