How to calculate the area of a right triangle

Divide the product of two right angle sides by two

In the general tense, when the subject is the singular third person, what is the change rule of the predicate verb?

The third person singular form of verbs
Generally, s is added at the end
2 ends with s, x, CH, SH, O and ends with es
3 ending with the consonant + y, change y into I and add es
4 have---has

How to draw the three heights of an obtuse triangle

Is it's time for followed by the original verb or the verb ing?

For is a preposition followed by a noun. When a verb appears after it, it needs to be changed into a gerund ing form. In fact, this is a common usage of prepositions. Other prepositions include about, in, on, at, from, off, etc

What is the role and status of science and technology in the process of human development?

Science and technology is a decisive force to promote the development of history. The history of science and technology is not only the history of human cognition of nature and the world, but also the history of human wisdom
The 20th century is a century of brilliant achievements in science and technology, as well as a century of growing maturity of human rationality. The vision of human observation of nature has expanded more than 100000 times in both micro and macro aspects: the understanding of the structure of matter has gone from molecules and atomic clusters larger than 10-10 meters to the interior of basic particles smaller than 10-18 meters, On the one hand, due to the in-depth development of various sciences, the natural world around us ranges from molecules, atoms and basic particles to cells, nuclei, chromosomes, DNA molecules and gene fragments, to the universe, celestial bodies, the earth's surface and the interior of the crust, On the other hand, due to the rise of interdisciplinary and interdisciplinary disciplines, the gap between various disciplines has been gradually filled, especially the emergence of molecular biology, which makes the gap between physical science and life science begin to disappear, With the rapid development of science and technology, the whole natural science is forming a developing, multi-level and comprehensive unity, The development of philosophy of science, history of science and sociology of science, as well as the alertness to the crisis of ecological environment and the formation of the concept of sustainable development, and the worry about the crisis that science and technology may bring to the development of human society, It marks that the breadth and depth of human reflection and Thinking on science and technology are increasing
In the first half of the 20th century, a series of scientific revolutions have not only profoundly changed human's understanding of the natural landscape of the world, but also led to the rapid development of economy and society. The establishment of relativity, quantum theory and information theory, the discovery of DNA double helix molecular model and quark model, the establishment of system theory and cybernetics, the earth plate model and the hypothesis of cosmic explosion, and the establishment of the earth plate model and the hypothesis of the universe explosion have all brought about great changes, It marks a new revolution in human understanding of matter, energy, space-time, information, life, earth and universe. Quantum chemistry, solid energy band theory, mass energy conversion principle, biological genetic center principle, stimulated radiation theory, feedback control and so on provide epoch-making key scientific principles for technological development, It has created a series of high-tech fields, such as information technology, new materials and manufacturing technology, biotechnology, new energy technology, marine technology and space technology, etc, It leads to the rapid development of computer hardware system from electron tube to transistor to integrated circuit and large-scale integrated circuit, and the development of its software system is based on Mathematics and logic; the combination of light emission and absorption theory from quantum theory and solid-state physics leads to the birth of laser, It has not only developed a variety of lasers, such as semiconductor lasers and gas lasers, but also derived free electron lasers and atomic lasers based on other physical principles, which led to the emergence of laser and optical communication technology; and gene control technology, including the shocking animal Kron technology, It is based on the double helix structure of DNA and the law of genetic center. The rapid development of science and the continuous development of social needs become the basis and driving force of technological progress. Technological innovation and technological invention based on science are constantly emerging, Technological progress also provides unprecedented means of experiment and observation for scientific discovery and research
The above-mentioned most important achievements in science and technology in the 20th century have had a great impact on human society, and are still constantly giving a strong impetus to social development, In the past 100 years, science and technology have shown an unprecedented and colorful picture. In the past 100 years, human beings have created a material civilization incomparable to that of the previous thousands of years, Science and technology has become a decisive factor in the comprehensive national strength and competitiveness of a country
(from BBC)

the teacher's desk is near the b__ .There's a p_ in our music room

1.　blackborad; piano
The teacher's desk is near the blackboard. There is a piano in our music classroom

As shown in the figure, in the triangle ABC, e is the midpoint of the middle line ad, and the extension line of be intersects AC at point F. if AC = 12cm, then AF =?

Through D as DG ‖ AC to be in G,
Then, EAF = EDG, EFA = EGD,
∵AE=DE,∴ΔEAF≌ΔEDG,
∴DG=AF,
∵ D is the midpoint of BC, ∵ DG = 1 / 2cf,
∴AF=1/2CF,
AF=1/3AC=4㎝.

What's the difference between clothes and clothing? Is it singular or plural?

Clothes is a plural noun without singular form. It can not be preceded by indefinite article or additive word, but it can be modified by some, these, those, many, fee, etc

Triangle ABC ≌ triangle ade, ∠ EAC = 30 °, finding the degree form of ∠ bad
Right

∵△ABC≌△ADE
∴∠BAC=∠DAE
∴∠BAC-∠DAC=∠DAE-∠DAC
That is, bad = EAC = 30 degree

In practical problems, under what circumstances should we seek the greatest common factor, and under what circumstances should we seek the least common multiple?
Such as the title

1） Fractional band unit: saw a 5 meter long wooden strip into three sections. How long is each section. Each section is 5 / 3 meters long
2） Seek the greatest common factor: three groups, 24, 8, 40 people respectively, all line up in the playground for recess exercises, each row stands up to more than one person, the three groups of people just finish. The greatest common factor of 24, 8, 40 is 8, each group stands up to 8 people
3） Least common multiple: a cuboid 4 cm long, 2 cm wide and 3 cm high. How many cuboids do you need to make a large cube
First, find out the least common multiple of 4,2,3, which is 12. The side length of the cube is 12 cm, 12 / 4 = 3,12 / 3 = 4,12 / 2 = 6,3 * 4 * 6 = 72. At least 72 small cuboids are needed to form a cube

How to calculate the area of a right triangle