Junior high school math formula 1: Pythagorean theorem 1 Pythagorean theorem The sum of squares of two right angles A and B of a right triangle is equal to the square of the hypotenuse C, that is, A 2+B 2 = C 2.
2 Inverse Theorem of Pythagorean Theorem If the lengths of three sides of a triangle A, B and C are related to A 2+B 2 = C 2, then the triangle is a right triangle.
I recommend reading: 20 17 summary of the most complete formulas of junior high school mathematical formula induction.
Junior high school math formula 2: the basic properties of quadrilateral theorem 3: the sum of the internal angles of quadrilateral is equal to 360 49, and the sum of the external angles of quadrilateral is equal to 360.
4 Theorem of the Sum of Interior Angles of Polygons The sum of interior angles of n polygons is equal to (n-2) × 180.
5 infer that the sum of the external angles of any polygon is equal to 360.
Junior high school math formula 3: parallelogram 6 parallelogram property theorem 1 parallelogram diagonal equality
7 parallelogram property theorem 2 The opposite sides of parallelogram are equal
It is inferred that the parallel segments sandwiched between two parallel lines are equal.
9 parallelogram property theorem 3 diagonal bisection of parallelogram.
10 parallelogram decision theorem 1 Two groups of quadrangles with equal diagonals are parallelograms.
1 1 parallelogram decision theorem 2 Two groups of parallelograms with equal opposite sides are parallelograms.
12 parallelogram decision theorem 3 quadrilaterals whose diagonals bisect each other are parallelograms.
13 parallelogram decision theorem 4 A group of parallelograms with equal opposite sides are parallelograms.
Junior high school math formula 4: rectangle 14 rectangle property theorem 1 all four corners of a rectangle are right angles.
15 rectangle property theorem 2 The diagonals of rectangles are equal.
16 rectangle judgment theorem 1 A quadrilateral with three right angles is a rectangle.
17 Rectangle Decision Theorem 2 Parallelograms with equal diagonals are rectangles.
Junior high school math formula 5: rhombus 18 rhombus property theorem 1 all four sides of the rhombus are equal.
19 diamond property theorem 2 The diagonals of the diamond are perpendicular to each other, and each diagonal bisects a set of diagonals.
20 diamond area = half of diagonal product, that is, S=(a×b)÷2.
2 1 diamond decision theorem 1 A quadrilateral with four equilateral sides is a diamond.
22 Diamond Decision Theorem 2 Parallelograms whose diagonals are perpendicular to each other are diamonds.
Junior high school math formula 6: Square 23 Square property theorem 1 All four corners of a square are right angles and all four sides are equal.
24 Square Property Theorem 2 Two diagonal lines of a square are equal and bisected vertically, and each diagonal line bisects a set of diagonal lines.
Junior high school math formula 7: trapezoid 25 theorem 1 congruence of two centrosymmetric figures.
Theorem 2 About two graphs with central symmetry, the connecting lines of symmetric points both pass through the symmetric center and are equally divided by the symmetric center.
27 Inverse Theorem If a straight line connecting the corresponding points of two graphs passes through a point and is bisected by the point, then the two graphs are symmetrical about the point.
28 isosceles trapezoid property theorem The two angles of isosceles trapezoid on the same base are equal.
The two diagonals of an isosceles trapezoid are equal.
30 isosceles trapezoid judgment theorem Two trapezoid with equal angles on the same base are isosceles trapezoid.
3 1 A trapezoid with equal diagonals is an isosceles trapezoid.
32 Theorem of Equal Segment of Parallel Lines If a group of parallel lines have equal segments on a straight line, then the segments on other straight lines are also equal.
Inference 1 passes through a straight line parallel to the trapezoid waist bottom, and the other waist will be equally divided.
Inference 2 A straight line passing through the midpoint of one side of a triangle and parallel to the other side will bisect the third side.
The midline theorem of triangle is parallel to the third side and equal to half of the third side.
36 Trapezoidal Mean Value Theorem The median line of a trapezoid is parallel to the two bottoms and equal to half of the sum of the two bottoms L = (a+b) ÷ 2s = l× h.
This is a summary of some junior high school math formulas, and there will be more. You can continue to pay attention to updates.