This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Cos unit circle. cos unit circle made by me under the public domain en Adrignola CommonsHelper Lmov en English Lmov Original upload log page en Cosunitcircle Lmov bytes no white background since ie doesn't like transparent Lmov bytes no unit circle made by me under the public domain Trigonometric circles