Inner angle of triangle on a circle made of consecutive three points is investigated. The quantity is known to show differences between chaotic series and random series analytically. In the paper, the inner angle properties for several series are calculated by numerical simulation. The chaotic series by the Bernoulli map, uniform random number series and normal random number series are used concretely. The inner angles for these series are compared. The formulas can be conformed numerically. In addition, it is found that the inner angles show little difference between uniform random series and normal one. (c) 2012 Published by Elsevier Ltd. Selection and/or Peer-review under responsibility of Takashi Hikihara and Tsutomu Kambe