Angle 1. Angle: An angle is a geometric object composed of two rays with a common endpoint.
2. Angle measurement unit: degrees, minutes and seconds.
3. Vertex: An angle consists of two rays with a common endpoint, and the common endpoint of the two rays is the vertex of the angle.
4. Angle comparison:
The angle (1) can be regarded as a ray rotating around its endpoint.
(2) Flat angle and fillet: A ray rotates around its endpoint. When the starting edge and the ending edge are on a straight line, the angle formed is called a straight angle. When it coincides with the starting edge again, the angle formed is a fillet. A right angle is equal to 108 degree, a rounded corner is equal to 360 degree, and a right angle is equal to 90 degree.
(3) bisector: A ray drawn from the vertex of an angle divides this angle into two equal angles, and this ray is called the bisector of this angle.
5. Complementary angle and complementary angle:
(1) Complementary angle: If the sum of two angles is 90 degrees, then these two angles are called complementary angles, which is called "complementation" for short.
Property: The complementary angles of equal angles are equal.
(2) Complementary angle: If the sum of two angles is 180 degrees, these two angles are called "complementary angle" or "remainder" for short.
Property: The complementary angles of equal angles are equal.
Algebra 1. Algebraic expression: the expression of the number of connections, and the letter indicating the number with the operation symbol "+-×××" is called algebraic expression (the number obtained by the letter should ensure that the formula in which it is located is meaningful, and the number obtained by the letter should also make real life or production meaningful; A single number or letter is also algebraic)
2. Some points for attention in column algebra:
Multiply (1) by letters, or multiply letters by letters, or omit;
(2) When the numbers are multiplied, they should still be multiplied by "×", but not by "×", and the multiplication sign cannot be omitted;
(3) When a number is multiplied by a letter, the number is usually written in front of the letter in the result. For example, a×5 should be written as 5a;
(4) When the band fraction is multiplied by letters, the band fraction should be changed to a false fraction, for example, a× should be written as a;
(5) When there is a division operation in the algebraic expression, the division method and the division method are generally connected by a fractional line, such as the form written in 3 A;
(6) The difference between A and B should be written in alphabetical order; If we only talk about the difference between two numbers, when we set the two numbers as A and B respectively, we should classify them and write them as a-b and B-A. ..
Inequality and inequality group (1) inequality
Using inequality symbols (
(2) the essence of inequality
① symmetry;
② Transitivity;
③ monotonicity of addition, that is, additivity of inequality in the same direction;
④ Monotonicity of multiplication;
⑤ Multiplicity of positive inequality in the same direction;
⑥ Positive inequalities can be multiplied;
⑦ Positive inequalities can be squared;
(3) One-dimensional linear inequality
A formula connected by an inequality symbol contains an unknown number whose degree is 1, whose coefficient is not 0, and whose left and right sides are algebraic expressions is called one-dimensional linear inequality.
(4) One-dimensional linear inequalities
The group of one-dimensional linear inequalities consists of several one-dimensional linear inequalities with the same unknowns.