# Tangent Lines and Secant Lines

*(This is about lines, you might want the tangent and secant functions)*

A **tangent**** line** just touches a curve at a point, matching the curve's slope there.
(From the Latin * tangens* "touching", like in the word "tangible".)

A **secant line** intersects two or more points on a curve. (From the Latin * secare* "cut or sever")

They are lines, so extend in both directions infinitely.

## Circle

On a circle they look like this:

There are three theorems of interest here: