two steps or

來源: 心如海 於 2010-04-10 06:11:51 [] [舊帖] [給我悄悄話] 閱讀數 : (179 bytes)

B=centre angle in radians
A=1/2*r^2(B-sinB), numerical solution of B then
H=r-rcos(B/2),

or
B=2arccos(1-H/r)

A=1/2*r^2{2arccos(1-H/r)-sin[2arccos(1-H/r)]}

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