Step 1 :

Find the value of the derivative of the function at the point by using straight edge and grid.

Straight edge method :

1). Select the point of the graph at which to find the derivative.

Plot the point of the graph of the function.

2). Draw a tangent line at using a ruler or straightedge. A tangent line is a line that touches the graph but does not intersect it at that point.

The graph is :

3). Select two points on the tangent line with clear - and - values.

Consider two points as and .

4). Subtract the first - value from the second.

5). Subtract the first - value from the second.

6). Divide the difference in - values by the difference in - values.

This is the slope of the tangent line, and is a good estimate of the derivative of our graph at the given point.

Solution :

Slope of the tangent line at is .