2. Evolution and origin. 3. Past facts.
History, for short, refers to the history of human society. It is a discipline that records and explains a series of historical events in the process of human activities, and it is also a mapping of the present era in many cases. If it is only summary and mapping, then history as an existence should disappear.
The problem of history is to discover the real past constantly, to speak with materials, and how people can become a negotiable problem in reality. [1] History is an extension.
History is the inheritance, accumulation and expansion of culture and the track of human civilization.
I have tried very hard to know the answer. I have tried my best.
How to judge the triangle congruence in the new teaching topic of mathematics in grade two (1) Teaching goal 1. Through mathematical activities such as drawing, operation, experiment and inquiry, the method of judging triangle congruence is explored. 2. Understand the methods of judging triangle congruence "ASA" and "AAS", and use them to judge the congruence of two triangles. Emphasis and difficulty: triangle determination methods "ASA" and "AAS" and their applications. Difficulties: the exploration of triangle judgment method. Teaching process 1. Review the introduction: 1 triangle. Called congruent triangles. 2. When two congruent triangles completely coincide, they are called corresponding vertices, corresponding edges and corresponding angles. 3.△ABC and △DEF are congruent triangles, denoted as. (Note: Write the letters corresponding to the vertices in the corresponding positions. ) 4. The nature of congruent triangles: Introduction: Is there any simpler way to judge congruent triangles besides definition? Second, the new teaching: 1. Experiments and explorations are known at Δ Δ ABC, ∠ B70 ∠ C50 BC 10 cm. Can a triangle be drawn according to the above conditions? If so, what should we do? (1) Draw ABC(2 that meets the above conditions on paper (2) Cut out the triangle you drew and compare it with the ones cut out by the students in the same group. Can these triangles completely coincide? (3) If the sizes of ∠B and ∠C are changed, please note: ∠ B ∠ B ∠ C.