This document provides an introduction to the concept of the tangent line and derivative. It defines the tangent line as the line that intersects a curve at exactly one point. It discusses how to approximate the slope of a tangent line using secant lines and taking the limit as the second point approaches the point of tangency. The derivative is defined as the formula that gives the slope of the tangent line at any point on a curve. It provides examples of using calculators to calculate derivatives and discusses how the graph of a derivative relates to properties of the original function such as maxima, minima and x-intercepts.

1. The Derivative and the Tangent Line Problem Lesson 3.1

2. Definition of Tan-gent

5. Animated Tangent

10. Animated Secant Line