## Complement

The word tangent comes from the Latin word tangent, which means touching. Two smooth curves are said to be tangent when they just touch at some point, usually without crossing one another. (For example, the functions $$y = 0$$ and $$y = x^2$$ are tangent at $$x = 0$$; Also $$y = 0$$ and $$y = x^3$$ are tangent at $$x = 0$$ even though they cross, because they sort of hug each other before crossing).