Written by the Fiveable Content Team โข Last updated September 2025
Written by the Fiveable Content Team โข Last updated September 2025
Definition
An inflection point is a point on a curve where the concavity changes from concave up to concave down or vice versa. At this point, the second derivative of the function is zero or undefined.
5 Must Know Facts For Your Next Test
An inflection point occurs where the second derivative of a function changes sign.
To confirm an inflection point, both the second derivative test and a change in concavity must be checked.
If $f''(x) = 0$ or $f''(x)$ is undefined at $x = c$, it is a candidate for an inflection point.
Concavity shifts from upward (concave up) to downward (concave down) or vice versa at an inflection point.
Not every point where the second derivative is zero is necessarily an inflection point; it must also show a change in concavity.
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Related terms
Second Derivative: The derivative of the first derivative of a function, often denoted as $f''(x)$, used to determine concavity and points of inflection.