\begin{definition}[Definition:Right Circular Cone/Base]
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Let $\triangle AOB$ be a right-angled triangle such that $\angle AOB$ is the right angle.
Let $K$ be the right circular cone formed by the rotation of $\triangle AOB$ around $OB$.
Let $BC$ be the circle described by $B$.
The '''base''' of $K$ is the plane surface enclosed by the circle $BC$.
{{EuclidSaid}}
:''{{Definition:Euclid's Definitions - Book XI/20 - Base of Cone}}''
{{EuclidDefRefNocat|XI|20|Base of Cone}}
Category:Definitions/Cones
\end{definition}