Noun
central angle (plural central angles)
(geometry) An angle positioned with its vertex at the center of a circle.
In particular, every inscribed angle that subtends a diameter is a right angle (since the central angle is 180 degrees). Source: Internet
Inscribed angles seeAlso Inscribed angle theorem An inscribed angle (examples are the blue and green angles in the figure) is exactly half the corresponding central angle (red). Source: Internet
The central angle between any two vertices of a perfect tetrahedron is arccos(−), or approximately 109.47°. Source: Internet