A central angle is an angle ∠A O C with endpoints A and C located on a circle's circumference and vertex O located at the circle's center . A central angle in a circle determines an arc arc A C. For an inscribed angle ∠A B C and central angle ∠A O C with the same endpoints, ∠A O C = 2∠A B C .

arc | full angle | inscribed angle | right angle | vertex angle