Algebraic expression 1 An expression formed by connecting numbers or letters representing numbers with operational symbols is called an algebraic expression. A single number or letter is also algebraic.
2. Replace the letters in the algebraic expression with numerical values, and the result calculated according to the operational relationship in the algebraic expression is called the value of the algebraic expression.
Algebraic expression 1 Algebraic expression: monomials and polynomials are collectively called algebraic expressions.
2. Monomial: The formula consisting of the product of numbers and letters is called monomial. A single number or letter is also a monomial.
3. coefficient; In the monomial, the numerical factor is called the coefficient of the monomial.
4. Times: The sum of the indices of all the letters in the monomial is called the times of this monomial.
5. Polynomial: The sum of several monomials is called polynomial.
6. Term: Each monomial that constitutes a polynomial is called a polynomial term.
7. Constant term: the term without letters is called constant term.
8. Degree of Polynomial: In a polynomial, the degree of the term with the highest degree is called the degree of this polynomial.
9. Similar terms: In polynomials, terms with the same letters and the same index of the same letters are called similar terms.
10. Merging similar items: Merging similar items in polynomials into one item is called merging similar items.
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.
Parallel lines 1. In the same plane, if two straight lines have no intersection point, then the two straight lines are parallel to each other, which is recorded as: a ∨ b.
2. Parallelism axiom: After passing a point outside a straight line, there is one and only one straight line parallel to this straight line.
3. If two straight lines are parallel to the third straight line, then the two straight lines are parallel to each other.
4. The method of judging that two straight lines are parallel:
(1) Two straight lines are cut by the third straight line. If congruent angles are equal, two straight lines are parallel. To put it simply: the same angle is equal and two straight lines are parallel.
(2) Two straight lines are cut by a third straight line. If the internal dislocation angles are equal, two straight lines are parallel. To put it simply: the internal dislocation angles are equal and the two straight lines are parallel.
(3) Two straight lines are cut by a third straight line. If they are complementary to each other, the two straight lines are parallel. To put it simply: the internal angles on the same side are complementary and the two straight lines are parallel.
triangle
1. triangle: A figure composed of three line segments that are not on the same line and are connected end to end is called a triangle.
2. Classification of triangles
3. Trilateral relationship of triangle: the sum of any two sides of triangle is greater than the third side, and the difference between any two sides is less than the third side.
4. Height: Draw a vertical line from the vertex of the triangle to the line where the opposite side is located, and the line segment between the vertex and the vertical foot is called the height of the triangle.
5. midline: in a triangle, the line segment connecting the vertex and the midpoint of its opposite side is called the midline of the triangle.
6. Angular bisector: The bisector of the inner angle of a triangle intersects the opposite side of this angle, and the line segment between the intersection of the vertex and this angle is called the angular bisector of the triangle.
7. Significance and practice of high line, middle line and angle bisector.
8. Stability of triangle: The shape of triangle is fixed, and this property of triangle is called stability of triangle.
9. Theorem of the sum of interior angles of triangle: the sum of three interior angles of triangle is equal to 180.
It is inferred that the two acute angles of 1 right triangle are complementary;
Inference 2: One outer angle of a triangle is equal to the sum of two non-adjacent inner angles;
Inference 3: One outer angle of a triangle is larger than any inner angle that is not adjacent to it;
The sum of the inner angles of a triangle is half of the sum of the outer angles.
10. External angle of triangle: the included angle between one side of triangle and the extension line of the other side is called the external angle of triangle.