S=a*a

(The area is equal to the square of the side length)

Rectangular area formula;

S=a*b (area equals length times width)

Triangle area formula;

Given that the base of a triangle is h, then S = Ah/2.

Given the three sides A, B, C and the half circumference P of a triangle, then S =

√[p(p

-

(p)

-

(p)

-

c)]

(Helen formula) (p=(a+b+c)/2)

And: (a+b+c)*(a+b-c)* 1/4.

Given the angle c between two sides a and b of a triangle, S = ABS Inc/2.

Let the three sides of a triangle be A, B and C respectively, and the radius of the inscribed circle be R.

Then the triangle area =(a+b+c)r/2.

Let the three sides of a triangle be A, B and C respectively, and the radius of the circumscribed circle be R.

Triangle area =abc/4r.

Given three sides a, b and c of a triangle, then s =

√{ 1/4[c^2a^2-((c^2+a^2-b^2)/2)^2]}

("triclinic orthogonality"

Qin Jiushao in Southern Song Dynasty)

Area formula of cylinder;

S bottom area = π r 2

S bottom area =π(d÷2)2

S bottom area =π(c÷π÷2)2

S lateral area =2π

r

h

S lateral area =πdh

S transverse area =ch

S surface area =

S lateral area+

2S bottom area

S surface area =

ch+2π(c÷π÷2)2

S surface area = π

d

h+2π(d÷2)2

S surface area =2πrh+2πr2

V=

Bottom area h

V

=

Pi?

r2

h

V

=

π(d÷2)2

h

V

=π(c÷π÷2)2

h

Remarks:

π≈3. 14

R is the radius,

D is the diameter, c is the bottom circumference, and v is the volume.