Data expansion:
Three lines are in one, that is, in an isosceles triangle (including an equilateral triangle), the bisector of the vertex, the median line of the bottom and the high line of the bottom coincide with each other, which is called three lines in one (the premise must be in an isosceles triangle, and other triangles are not applicable).
Isosceles triangle:
An isosceles triangle is a triangle with at least two equilateral sides. Two equal sides are called the waist of this triangle. In an isosceles triangle, two equal sides are called waist and the other side is called bottom. The angle between the two waists is called the top angle, and the angle between the waist and the bottom edge is called the bottom angle. The two base angles of an isosceles triangle are equal (abbreviated as "equilateral angles").
Introduction to mathematics:
Mathematics [English: Mathematics, from ancient Greece μ? θξμα(máthēma)； Often abbreviated as math or maths], it is a discipline that studies concepts such as quantity, structure, change, space and information.
Mathematics is a universal means for human beings to strictly describe and deduce the abstract structure and mode of things, and can be applied to any problem in the real world. All mathematical objects are artificially defined in essence. In this sense, mathematics belongs to formal science, not natural science. Different mathematicians and philosophers have a series of views on the exact scope and definition of mathematics.
Rigidity:
Mathematical language is also difficult for beginners. How to make these words have more accurate meanings than everyday language also puzzles beginners. For example, the words "open" and "domain" have special meanings in mathematics. Mathematical terms also include proper nouns such as embryo and integrability. But these special symbols and terms are used for a reason: mathematics needs accuracy more than everyday language. Mathematicians call this requirement for linguistic and logical accuracy "rigor".
Mathematics is a universal means for human beings to strictly describe the abstract structure and mode of things, and can be applied to any problem in the real world. In this sense, mathematics belongs to formal science, not natural science. All mathematical objects are artificially defined in essence. They do not exist in nature, but only in human thinking and ideas.
Therefore, the correctness of mathematical propositions can not be tested by repeated experiments, observations or measurements, like physics, chemistry and other natural sciences whose purpose is to study natural phenomena, but can be directly proved by strict logical reasoning. Once the conclusion is proved by logical reasoning, then the conclusion is correct.