Induction formula In triangle ABC, sin [(a + B-C) / 2] = sin [(a-b + C) / 2], try to judge the shape of triangle ABC

Induction formula In triangle ABC, sin [(a + B-C) / 2] = sin [(a-b + C) / 2], try to judge the shape of triangle ABC

sin[(A+B-C)/2]=sin[(A-B+C)/2],
There are only two cases
(A+B-C)/2=(A-B+C)/2
Or (a + B-C) / 2 = π - (a-b + C) / 2
Therefore, it is divided into the following two situations
1. When (a + B-C) / 2 = (a-b + C) / 2
A+B-C=A-B+C
B=C
ABC is an isosceles triangle
2. When [(a + B-C) / 2 = π - (a-b + C) / 2
A+B-C=2π-A+B-C
2A=2π
A=π
At this time, it can not form a triangle, so the hypothesis is not true
In conclusion, ABC is an isosceles triangle

10. (2010-8226; Wenzhou, Zhejiang, senior 3-2 test) the following statements about the military aircraft department are correct:
A. During the reign of Kangxi, it was set up to meet the needs of military affairs in Northwest China. B. its initial function was to deal with military affairs and other government affairs
C. The military aircraft ministers are appointed by the important ministers in the court. D. is more efficient, but the decision-making is more closed
Why not choose B?

The military aircraft department was first set up by Emperor Yongzheng in order to deal with military affairs quickly, with the purpose of strengthening imperial power, reducing intermediate links and improving the efficiency of handling military affairs. Therefore, at the beginning, its function was only to deal with military affairs, and other government affairs were not important, so it did not choose B
Objective: to strengthen imperial power and improve military and political efficiency
Functions: in the early days, it was only limited to dealing with emergency military affairs, and later it developed into an arbitrary organization for the emperor to deal with various affairs, marking the peak of imperial power

According to the inscriptions in Yuding, marquis og rebelled against Zhou Dynasty, and King Li ordered Yu to go out to battle and win his king
A. The enfeoffment system tended to decline and could still maintain the royal power. B. the patriarchal system began to collapse
C. The power of the king of Zhou was strengthened and the power of the king of Zhou was weakened
Shandong is also known as the land of Qilu, and Yanzhao is another name for Hebei Province
A. County system in Qin Dynasty B. enfeoffment system in Western Zhou Dynasty
C. The patriarchal system of the Western Zhou Dynasty D. the centralized system of the Qin Dynasty
Please elaborate on why,

1A 2B
The second individual thinks that the choice of B is because the six states Qi, Chu, Yan, Han, Zhao and Wei were unified in the Qin Dynasty, which means that the statement of Qi, Lu, Yan and Zhao should have existed at that time, and it should not have originated from the county system of the Qin Dynasty

1. About the political system of the Western Zhou Dynasty and its relationship, the correct statement is: ① patriarchal system and enfeoffment system are both exterior and interior; ② patriarchal system takes the eldest son inheritance system as the core; ③ through enfeoffment system and patriarchal system, a hierarchical system is established; ④ the whole system has maintained the stability of the Zhou Dynasty for a long time. What's wrong with A123 b124 C23 d1234 4? 2, A points out the essential difference between the enfeoffment system and the county system. B affirms the role of the local administrative system in the Qin Dynasty,

The system of enfeoffment in the late Western Zhou Dynasty formed a situation of separatism, which resulted in the turbulent Eastern Zhou Dynasty, that is, the spring and Autumn period and the Warring States period
The essential difference in history generally refers to the difference in economic system. The enfeoffment system represents the slavery economy, affirms the advantages of the county system, but does not emphasize their essential difference, so B

Two compulsory subjects of high school history
US Secretary of state Marshall once declared on the "European recovery plan" that "the purpose of our policy is to restore the world's effective economic system, so that the political and social conditions for the existence of a free system can emerge." the so-called "world's effective economic system" refers to []
A. Free competition system characterized by mercantilism
B. Free trade system in the world market
C. The social welfare system vigorously promoted by the state
D. Market economy system based on private ownership
Why not choose B, but d?

”The so-called "effective economic system in the world" at that time, after the end of World War II, the capitalist countries led by the United States and the Eastern European countries led by the Soviet Union were engaged in economic and military competitions. Therefore, from the economic level, public ownership: socialist countries, private ownership: capitalist countries