Central Angle

$\begin{figure}\begin{center}\BoxedEPSF{CentralInscribedAngle.epsf}\end{center}\end{figure}$

An Angle having its Vertex at a Circle's center which is formed by two points on the Circle's Circumference. For angles with the same endpoints,

$\begin{displaymath} \theta_c=2\theta_i, \end{displaymath}$

where $\theta_i$ is the Inscribed Angle.

References

Pedoe, D. Circles: A Mathematical View, rev. ed. Washington, DC: Math. Assoc. Amer., pp. xxi-xxii, 1995.