Show equation of tangent

[pinkman]

(11-14-2019 01:55 PM)CyberAngel Wrote:  Could you kindly establish the exact 3rd degree polynomial
that you used in the picture or any other
that I can truly test.
Note that a derivative of a 3rd degree polynomial is a 2nd degree polynomial
a straight like is a 1st degree polynomial - one needs f''(x) in terms of derivation

In the picture I used : F1(X)=X^3+0.5*X^2-2*X-4
I randomly showed the tangent for X=1.07 (right part of the split view).
The SLOPE for x=1.07 is 2.5047 (shown in lower part of display, and also true when calculated from the derivative 3*X^2+X-2 with X=1.07), but to draw the tangent, in the symbolic view you just have to write for F2 : SLOPE(F1,1.07)*(X-1.07)+F1(1.07)

I don't understand your reflexion about the derivative, as a tangent is always a straight line, whatever the function is.