Judgement theorem of isosceles triangle If a triangle has two equal angles, then the opposite sides of the two angles are also equal (equal angles and equal sides); The bisector of an angle is the set of all points with equal distance to both sides of the angle.

Math Area Formula of Grade Two The common geometric area formulas in junior high school are as follows:

Rectangular area = length × width, S=ab

Square area = side length × side length, S=a?

Triangle area = base × height ÷2, S=ah/2 parallelogram area = base × height, S=ah trapezoid area = (upper base+lower base) × height ÷2, S= 1/2(a+b)h circular area = radius × radius × π. /360

Side area of right-angle prism: S=c*h

Side area of oblique prism: S = c'* h

Side area of a regular pyramid: S= 1/2c*h'

Side area of prism: S = 1/2(c+c')h'

Area of frustum side: s =1/2 (c+c') l = pi (r+r) l.

Surface area of the ball: S=4pi*r2.

Area of cylinder side: s = c * h = 2pi * h

The lateral area of the cone: s =1/2 * c * l = pi * r * l.

Arc length formula: l=a*r.a is the radian number r >； of the central angle; 0

Sector area formula: s =1/2 * l * r.

Cone volume formula: V= 1/3*S*H

Cone volume formula: V= 1/3*pi*r2h.

Oblique prism volume: V=S'L Note: where s' is the straight cross-sectional area and l is the side length.

Complete set of necessary formulas for junior two mathematics 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. Complete cubic sum formula: 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. the formula of cubic sum of three terms: a? +b？ +c？ -3abc=(a+b+c)(a？ +b？ +c？ -ab-bc-ac).