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.
Tangential quadrilateral.svg en Tangential quadrilateral Redrawn after bitmap image at en Image Tangentialquad Own David Eppstein Files by User David Eppstein from en Tangential quadrilaterals
Page 2023 Free-images.com. All images are Public Domain