Two-angle sum formula

1、sin(A+B)= Sina cosb+cosAsinBsin(A-B)= Sina cosb-sinBcosA

2、cos(A+B)= cosa cosb-Sina sinb cos(A-B)= cosa cosb+Sina sinb

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

Double angle formula

1、tan2A = 2 tana/( 1-tan2A)ctg2A =(ctg2A- 1)/2c TGA

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

Second, the common formula of factorization

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

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

3. Cubes and formulas: A? +b？ =(a+b)(a？ -ab+b？ )。

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

5. Complete cubes and formulas: a? +3a？ b+3ab？ +b？ =(a+b)？ .

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

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

8. Three cubes and formulas: A? +b？ +c？ -3abc=(a+b+c)(a？ +b？ +c？ -ab-bc-ac).

Three, the area formula of common graphics

1, rectangular area = length× width S=ab

2. Square area = side length x side length S=a?

3. The area of triangle = base × height ÷2S=ah÷2.

4. parallelogram area = bottom x height S=ah.

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

6. Area of circle = π× radius× radius