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