HP42s first major program (Double Integral) Best way to approach?

[J-F Garnier]

(05-27-2020 06:38 AM)Paul Dale Wrote:  Ángel, the 15C manual talks about available registers for solve and integrate. I'm surprised that these aren't recursive.

An attempt to integrate or solve recursively produces the Error 7 on the 15C, which is SOLVE(SOLVE) or INTEG(INTEG) as indicated on the back of the 15C :-)

The HP-71B Math ROM was the first to allow recursive solve or integrate functions, up to 5 levels. It was a major design challenge, as related in the HP Journal article.

J-F