Plus42 Equations, Preview Release

[Albert Chan]

(11-30-2021 03:25 PM)Vincent Weber Wrote:  In the real domain, SIN(X) is always ≤=1, -SIN(X) ≥ -1, 1-SIN(X)≥0, and (1-SIN(X))^3≥0, so the equation result is always ≥1, and therefore never equal to 0. How on earth can the HP-71B find a real root to this ??

Not real root, but extremum. We expected minimum when x = PI/2 + 2*K*PI

1+(1-SIN(PI/2+2*K*PI))^3 = 1+0 = 1, close to HP-71B FVALUE of 1.00000000001

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Another Plus42 example, with expected behavior (no complex number result)

"K=X/COSH(X)", go in "CALC" 1 "K" "X" --> 1.19967864026 "Extremum"

Enter "K" "K" --> 0.662743419349 (see Catenoid soap bubbles thread, H/R when bubble pop)