A digression around VA's SRC #012b

[Albert Chan]

(11-27-2022 03:45 PM)Albert Chan Wrote:  FNROOT is interpolating the secant line for root, from points (x1,y1), (x2,y2)

My mistake. From HP Journal, July 1984

Quote:The search for a root proceeds by bent-secant, quadratic interpolation, and minima-bounding methods, depending on the detected shape of the function.

FNROOT always return something. Confirmation of root, FVALUE ≈ 0, is required.

Quote:FNBOOT will return a value when it finds a root, a local minimum of absolute value, or a pair of neighboring machine-representable numbers across which the function changes sign, when the search leads out of the range of representable numbers, or when quadratic interpolation has been used eight times in succession.