Definition:Cone/Apex
< Definition:Cone(Redirected from Definition:Apex of Cone)
Jump to navigation
Jump to search
Definition
Consider a cone consisting of the set of all straight lines joining the boundary of a plane figure $PQR$ to a point $A$ not in the same plane of $PQR$:
In the above diagram, the point $A$ is known as the apex of the cone.
Also known as
The apex of a cone is also known as its vertex.
Also see
Linguistic Note
The plural of apex is apices, which is pronounced ay-pi-seez.
The form apexes can often be seen, but this is technically incorrect.
Compare vertex.
Hence the colloquial phrase base over apex as the description of a particularly flamboyant physical tumble.
Sources
- 1933: D.M.Y. Sommerville: Analytical Conics (3rd ed.) ... (previous) ... (next): Chapter $\text {IV}$. The Ellipse: $1$.
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): Entry: vertex