The relationship between the sides of a right triangle is 1, the sum of the two sides of the triangle is greater than the third side, and the difference between the two sides is smaller than the third side. (The sum of two sides of a triangle is greater than two of the third side, indicating two smaller sides, and the difference between the two sides is less than the third side, indicating two larger sides. )
2. In a right triangle, if an angle is equal to 30 degrees, then the right side opposite to the 30-degree angle is half of the hypotenuse. The sum of squares of two right-angled sides of a right-angled triangle is equal to the square of the hypotenuse (Pythagorean theorem). Inverse Theorem of Pythagorean Theorem: If the lengths of three sides of triangle A, B and C satisfy a? +b？ =c？ Then this triangle is a right triangle.
3. The midline of the hypotenuse of a right triangle is equal to half of the hypotenuse.
4. The three bisectors of the triangle intersect at one point, the straight lines of the three high lines intersect at one point, and the three middle lines intersect at one point.
5. The sum of squares of the lengths of the three center lines of a triangle is equal to 3/4 of the sum of squares of the lengths of its three sides.
6. The area of a triangle with equal base and height is equal.
7. The area ratio of equilateral triangles is equal to their height ratio, and the area ratio of equilateral triangles is equal to their base ratio.
8. Any midline of a triangle divides the triangle into two triangles with equal areas.
9. The bisector of the top angle of an isosceles triangle is on a straight line with the height and the center line on the bottom edge (the three lines are one).
Geometric formula of junior high school: straight line
1 The complementary angles of the same angle or the same angle are equal.
One and only one straight line is perpendicular to the known straight line.
There is only one straight line between two points.
The line segment between two points is the shortest.
The complementary angles of the same angle or the same angle are equal.
Of all the line segments connecting a point outside the straight line with points on the straight line, the vertical line segment is the shortest.
7 Parallel axiom passes through a point outside a straight line, and there is only one straight line parallel to this straight line.
If both lines are parallel to the third line, the two lines are also parallel to each other.
Further reading: summary of junior high school geometry theorem * * * junior high school geometry formula: angle
The same angle is equal and two straight lines are parallel.
The internal dislocation angles of 10 are equal, and the two straight lines are parallel.
1 1 are complementary and two straight lines are parallel.
12 Two straight lines are parallel and have the same angle.
13 two straight lines are parallel, and the internal dislocation angles are equal.
14 Two straight lines are parallel and complementary.
Junior high school geometric formula: triangle
Theorem 15 The sum of two sides of a triangle is greater than the third side.
16 infers that the difference between two sides of a triangle is smaller than the third side.
The sum of the internal angles of 17 triangle is equal to 180.
18 infers that the two acute angles of 1 right triangle are complementary.
19 Inference 2 An outer angle of a triangle is equal to the sum of two non-adjacent inner angles.
Inference 3 The outer angle of a triangle is greater than any inner angle that is not adjacent to it.
2 1 congruent triangles has equal sides and angles.
The corner axiom has two triangles with equal angles.
The axiom of angles and angles has two angles and two triangles with equal corresponding sides.
It is inferred that there are two angles, and the opposite side of one angle corresponds to the congruence of two triangles.
The 25-sided axiom has two triangles corresponding to three sides.
The axiom of hypotenuse and right-angled side has the coincidence of hypotenuse and right-angled side corresponding to two right-angled triangles.
Theorem 1 The distance between a point on the bisector of an angle and both sides of the angle is equal.
Theorem 2 is a point with equal distance on both sides of an angle, which is on the bisector of this angle.
The bisector of an angle 29 is the set of all points with equal distance to both sides of the angle.