The formula of the circumference of a circle: C=πd, the diameter of the circle is 24cm, and the circumference of the circle C=24π≈75.36cm.

Derivation of the formula of the circumference of a circle (this aspect involves arc differentiation)

Let the parameter equation of a circle be.

Integral of a circle in a week

Substitute, available

Namely.

Extended data:

Formula for calculating circle area: or

Find the diameter from the area of a circle:?

Divide a circle into several equal parts and you can make an approximate rectangle. The width of a rectangle corresponds to the radius of a circle.

Transverse area of cone (L is the length of bus)

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

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

Radius of cone bottom surface r=nR/360(r is the radius of bottom surface) (N is the central angle)

R is the radius of the sector, n is the degree of the central angle of the arc, π is pi, and L is the arc length corresponding to the sector. You can also divide the area of the circle where the sector is located by 360 and multiply it by the angle n of the central angle of the sector, as follows: (L is the arc length and R is the sector radius)

Deduction process: S=πr? ×L/2πr=LR/2，(L=│α│ R).

References:

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