How Does the Derivative of a Cubic Function Result in a Tangent Line?

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Discussion Overview

The discussion revolves around understanding the concept of derivatives, specifically how the derivative of a cubic function, such as y=x^3, relates to the tangent line at a given point on the curve. Participants explore the fundamental nature of derivatives and their implications for tangent lines in the context of polynomial functions.

Discussion Character

  • Conceptual clarification, Technical explanation

Main Points Raised

  • One participant expresses confusion about how the derivative of a cubic function can yield a tangent line, contrasting it with the simpler case of a quadratic function.
  • Another participant clarifies that the first derivative provides the slope of the tangent line rather than the tangent line itself, introducing the point-slope formula for constructing the tangent line.
  • A participant seeks confirmation that the derivative gives the slope (m) needed for the equation of a straight line.
  • There is an affirmation that the derivative evaluated at the x-coordinate of the tangent point indeed gives the slope of the tangent line.

Areas of Agreement / Disagreement

Participants generally agree on the role of the derivative in determining the slope of the tangent line, though initial confusion about the concept is evident. The discussion does not present any competing views or unresolved disagreements.

Contextual Notes

The discussion assumes familiarity with basic calculus concepts such as derivatives and tangent lines, and it does not address potential limitations in understanding the geometric interpretation of derivatives.

Who May Find This Useful

Readers interested in calculus, particularly those grappling with the concepts of derivatives and tangent lines in polynomial functions.

tenman
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I'm have trouble understanding a fundamental question of a derivative. So a derivate gives me a tangent line at any given point on a function.

this makes sense for me for a function y=x^2 because the derivative is y'=2x which is a straight line function.

But what about y=x^3 where the derivative is y'=3x^2 this function is a parabola how can a parabola give me a tangent line?

I'm having trouble understand this very basic concept
 
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The first derivative of a function gives you the slope of the tangent line, not the tangent line itself. Thus,for some function $f(x)$, the tangent line (using the point-slope formula) at the point $(x_0,f(x_0))$ is given by:

$$y=f'(x_0)(x-x_0)+f(x_0)$$
 
Ahh ok thanks I think I get it now.

So the general formula for a straight line is y=mx+c

are you saying that the derivative of a function gives you the m value needed to plug into the straight line formula?
 
tenman said:
Ahh ok thanks I think I get it now.

So the general formula for a straight line is y=mx+c

are you saying that the derivative of a function gives you the m value needed to plug into the straight line formula?

Yes, the derivative of the function evaluated at the $x$-coordinate of the tangent point will give you the slope $m$ of the tangent line. :)
 
Thanks heaps for that!
 

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