So we have the approximate equation
1/3 x^3 + O(x^5) = 1/3 w^3
=> x^3 ( 1 + O(x^2) ) = w^3
=> x ( 1 + O(x^2) ) = w
=> x = w ( 1 + O(x^2) ) = w ( 1 + O(w^2) ) = w + O(w^3).
Using more terms of the series of tan we get the relation
2 2 29 4 14 6 8
x = w ( 1 - -- x - ---- x - ---- x + O(x ) )
15 1575 3375
____________
3 / x^3 / 3
= w \ / ------------
\/ tan(x) - x
x0 = w + O(w^3)
x1 = w - 2/15 w^3 + O(w^5)
x2 = w - 2/15 w^3 + 3/175 w^5 + O(w^7)
. . .
2 3 3 5 2 7 16 9 11
x = w - -- w + --- w - ---- w - ------ w + O(w )
15 175 1575 202125
Therefore the equation 1 - sin(x)/x = d has the solution
_____ 3 321 2 3197 3 445617 4 1766784699 5 6
x = \/ 6 d ( 1 + -- d + ---- d + ------ d + -------- d + ------------ d + O(d ) )
20 5600 112000 27596800 179379200000
Piece of **** if you ask me.....