Estimate slope of tangent line by calculating slopes of secant lines

In this example problem, we want to estimate the slope of a tangent line to a given function graph. We use two points on the graph and calculate the slope of their secant line by using the slope formula. We choose our second point closer and closer to the point that we are attempting to estimate the tangent line. These secant lines are drawn onto the graph for a visual representation, so that we can see them getting closer to the tangent line that is also drawn on the graph.