Perimeter =2πR,

circle

R radius

diameter

C=πd=2πr

S=πr2

=πd2/4

department

R- sector radius

Degree of central angle

C=2r+2πr×(a/360)

S=πr2×(a/360)

arch form

L- arc length

B chord length

H vector height

R radius

Degree of α -central angle

s = R2/2(ωα/ 180-sinα)

=r2arccos[(r-h)/r]

-

(r-h)(2rh-h2) 1/2

=παr2/360

-

b/2 [r2-(b/2)2] 1/2

=r(l-b)/2

+

bh/2

≈2bh/3

ring

R- excircle radius

R- radius of inner circle

D- cylinder diameter

Diameter of inner circle

S=π(R2-r2)

=π(D2-d2)/4