b^2<=x^2 + y^2<=a^2

annular disk | disk with circular hole | hollow circle

0

A = π (a^2 - b^2)

x^_ = (0, 0)

J_x invisible comma x = 1/4 π (a^4 - b^4)

J_y invisible comma y = 1/4 π (a^4 - b^4)

J_zz = 1/2 π (a^4 - b^4)

J_x invisible comma y = 0

r_x = 1/2 sqrt(a^2 + b^2) r_y = 1/2 sqrt(a^2 + b^2)

K = 1/2 π (a^4 - b^4)

p = 2 π (a + b)

2 a

χ = (2 (a^2 cos^(-1)(b/a) - b sqrt(a^2 - b^2)))/(π (a^2 - b^2))

concave laminae | laminae of constant width | laminae with holes