# [plt-scheme] HtDP Exercise 23.4.1

On Feb 10, 2009, at 9:53 AM, David Yrueta wrote:
>* Hi Matthias --
*>*
*>* David, it is entirely safe to navigate around the mathematics
*>* sections in the book
*>*
*>* Yes, but I can't resist the challenge of tackling and hopefully
*>* solving an explicitly "mathematical" problem which I always
*>* considered beyond my reach :) (which is why I'm up at 5:30 am
*>* taking a whack at this thing!).
*>*
*>* I looked at the link sent to me by Thomas Chust and came up with
*>* this version of integrate-kepler (before reading your comments
*>* below, which I will):
*>*
*>* (define (integrate-kepler f left right)
*>* (local ((define (area-of-trap a b1 b2)
*>* (* a ( / ( + (f b1) (f b2)) 2)))
*>* (define midpoint ( / (+ right left) 2))
*>* (define alt-left (- midpoint left))
*>* (define alt-right (- right midpoint)))
*>* (+ (area-of-trap alt-left left midpoint)
*>* (area-of-trap alt-right midpoint right))))
*>*
*>* Am I in the ballpark?
*
Where are your examples? Tests? :-)