(42S) Determine Circle From Three Given Points

[Dieter]

(07-17-2018 01:21 PM)Thomas Klemm Wrote:  The HP-42S allows to use complex numbers to solve the problem.

Hey, that's a really great new approach! Hats off!

(07-17-2018 01:21 PM)Thomas Klemm Wrote:  The radius of the circle isn't calculated. But that should be easy now that we know the center.

The simplest way of calculating the radius may be storing one of the points (as a complex number) at the beginning (insert STO "P" between line 01 and 02), and add a final ENTER RCL–"P" ABS at the end. This will return the center coordinates in Y and the radius in X:


 1  ENTER  4  COMPLEX
-1  ENTER  2  COMPLEX
 4  ENTER -3  COMPLEX
XEQ "CENTER"
=>
2,5 i0,5
3,80788655...


Dieter