Tangent Line as a Limit of Secant Lines

Instructions

• Use the drop down menu to select a function.
• The blue line is a secant to the function through points $A$ and $B$.
• The green line is a tangent to the function through point $A$.
• Drag points $A$ and $B$ to see how the slopes of the tangent and secant lines change.
• Drag point $B$ closer to point $A$ and see what happens to the slopes of the secant and tangent lines as $B$ approaches $A$.