Breaking point
From HandWiki
angle point
A singular point of a plane curve with the property that two branches of the curve end in it in such a way that each has a (one-sided) tangent at the point different from the other. For example, the origin is a breaking point of the curve $y=x/(1+e^{1/x})$ (see Fig.). The left and right derivatives are different at a breaking point.
<img style="border:1px solid;" src="https://www.encyclopediaofmath.org/legacyimages/common_img/b017630a.gif" />
Figure: b017630a
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