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:
Tubular neighborhood. Illustration of en Tubular neighborhood Made with en Matlab Oleg Alexandrov June UTC Public domain Source code MATLAB illustration of tubular neighborhood function main pi linspace sin ll length of lines perpendicular to the curve thinline thickline will draw lines perpendicular to the graph of at points