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

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

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

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

5. Sector arc length L= central angle (arc system) ×R= nπR/ 180(θ is central angle) (r is sector radius).

6. Sector area S=nπ R? /360=LR/2(L is the arc length of the sector).

7. The radius of the cone bottom surface r=nR/360(r is the radius of the bottom surface) (n is the central angle).