WP 34S solve an integral

[Dieter]

(04-23-2015 09:05 PM)BarryMead Wrote:  

Code:

...
LBL 00
0                       //Lower bound of integral (from zero to solve guess)
x <> Y
∫ 01
RCL 00                  //Value to solve for (to get upper integral bound)
x <> Y
-                       //Integral function returns zero when integral equals R00 target value
RTN
...

Of course it doesn't matter whether you solve ∫ – 10 = 0 or 10 – ∫ = 0, so the second x<>y is not required, and a simple RCL–00 will do as well.
Or, even shorter:

Code:

LBL 00
 0
∫ 01      // ∫ from x to 0 = –∫ from 0 to x 
RCL+ 00   // 10 – ∫
RTN

Sorry for the nitpicking. ;-)

(04-23-2015 09:05 PM)BarryMead Wrote:  Then Press 0 Enter 5 Enter 10 A (Solves for X where the integral of x² from zero to X = 10) = 3.10723250595
Try 3 Enter 7 Enter 20 A (Solves for X where integral of x² from zero to X = 20) = 3.91486764117

FTR: the exact solutions are the cube roots of 3·10 resp. 3·20.

Dieter