Concept of a Curve. (Chapter 3) Important notes. Schaum's outlines of differential geometry.

 https://www.facebook.com/100076036906367/posts/pfbid02HBzHSqBauFnPWgg95MyQtMMK6ffkDXr9Yjgmnf979DjUR31FpnyUNtLaDgPGfiuAl/?app=fbl