## cuspIn mathematics, a point on a curve where two branches, coming from different directions, meet and have a common tangent. If the two branches of the curve approach the tangent from opposite sides the cusp is called a keratoid (from the Greek kera
for horn) or first-order cusp. This is the case, for example,
with the curve given by the equation y^{2} = x^{2}y
+ x^{5}. If the two branches of the curve approach the
tangent from the same side the result is a ramphoid or
second-order cusp. The curvature
at a cusp is infinite. "Cusp" derives from the Latin cuspis
for sharp. Outside of mathematics, the points of a crescent moon are called
cusps and the sharp pointed premolar teeth of children are known as bicuspids.
## Related category• PLANE CURVES | |||||

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