死算出來的。一直沒想出純幾何方法求h

h = hight of the arc. and A = 2*Pi*R*h

L = tangent line. 2a = chord.

L^2 = r*(2R + r), a^2 = h*(2R - h), and substitue them in

(h + r)^2 = L^2 - a^2

h = Rr/(2(R+r)).

 

所有跟帖： 

• You Rit. We also can use similar tringles and ...getting h(r-h)= -jinjing- ♀ (0 bytes) () 08/15/2011 postreply 16:44:33

• (R+r-h)^2=(R+r)^2-R^2-h^2,... -jinjing- ♀ (0 bytes) () 08/15/2011 postreply 17:31:02

• Sorry, It should be: (R+r-h)h=(R+r)^2-R^2-h^2,... -jinjing- ♀ (0 bytes) () 08/15/2011 postreply 17:33:49