死算出来的。一直没想出纯几何方法求h

wxcfan123 2011-08-15 14:39:14 ( reads)

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)).

跟帖(3)

You Rit. We also can use similar tringles and ...getting h(r-h)=

(R+r-h)^2=(R+r)^2-R^2-h^2,...

Sorry, It should be: (R+r-h)h=(R+r)^2-R^2-h^2,...