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Summary of junior high school mathematics formula
Junior high school students should master basic formulas when learning mathematics. The following summarizes the junior high school mathematics formula, hoping to help everyone learn mathematics.

The formula of the sum of two angles of trigonometric function

sin(A+B)=sinAcosB+cosAsinB

sin(A-B)=sinAcosB-sinBcosA

cos(A+B)=cosAcosB-sinAsinB

cos(A-B)=cosAcosB+sinAsinB

tan(A+B)=(tanA+tanB)/( 1-tanA tanB)

tan(A-B)=(tanA-tanB)/( 1+tanA tanB)

ctg(A+B)=(ctgActgB- 1)/(ctg B+ctgA)

ctg(A-B)=(ctgActgB+ 1)/(ctg b-ctgA)

Double angle formula

tan2A=2tanA/( 1-tan2A)

ctg2A=(ctg2A- 1)/2ctga

cos2a = cos2a-sin2a = 2 cos2a- 1 = 1-2 sin2a

half-angle formula

sin(A/2)=√(( 1-cosA)/2)

sin(A/2)=-√(( 1-cosA)/2)

cos(A/2)=√(( 1+cosA)/2)

cos(A/2)=-√(( 1+cosA)/2)

tan(A/2)=√(( 1-cosA)/(( 1+cosA))

tan(A/2)=-√(( 1-cosA)/(( 1+cosA))

ctg(A/2)=√(( 1+cosA)/(( 1-cosA))

ctg(A/2)=-√(( 1+cosA)/(( 1-cosA))

Sum difference product

2sinAcosB=sin(A+B)+sin(A-B)

2cosAsinB=sin(A+B)-sin(A-B)

2cosAcosB=cos(A+B)-sin(A-B)

-2sinAsinB=cos(A+B)-cos(A-B)

sinA+sinB = 2 sin((A+B)/2)cos((A-B)/2

cosA+cosB = 2cos((A+B)/2)sin((A-B)/2)

tanA+tanB=sin(A+B)/cosAcosB

tanA-tanB=sin(A-B)/cosAcosB

ctgA+ctgBsin(A+B)/sinAsinB

-ctgA+ctgBsin(A+B)/sinAsinB

Rectangular common graphic area formula = length× width S = ab

Area of a square = side length × side length S = a?

Area of triangle = base × height ÷2 S=ah÷2.

Area of parallelogram = base × height S=ah

Trapezoidal area = (upper bottom+lower bottom) × height ÷2 S=(a+b)h÷2.

Area of circle = π× radius× radius

Factorization formula square difference formula: a? -B? =(a+b)(a-b).

Complete square formula: a? +2ab+b? =(a+b)? .

Cubic sum formula: a? +b? =(a+b)(a? -ab+b? )。

Cubic difference formula: a? -B? =(a-b)(a? +ab+b? )。

Complete cubic sum formula: a? +3a? b+3ab? +b? =(a+b)? .

Complete cubic difference formula: a? -3a? b+3ab? -B? =(a-b)? .

Three complete square formulas: a? +b? +c? +2ab+2bc+2ac=(a+b+c)? .

Formula of cubic sum of three terms: a? +b? +c? -3abc=(a+b+c)(a? +b? +c? -ab-bc-ac).

Volume formula of the ball Volume formula of the ball: the volume of the ball with radius r.

The formula is: v = (4/3) π r 3 (three quarters times π times the radius of the cube).

V = (1/6) π d 3 (one sixth times π times the third power of diameter)