The dy/dx command finds a numeric derivative, which approximates the first derivative of an expression with respect to the x variable at the trace cursor location while viewing a graph.
While viewing the graph of a function, press to view the MATH functions.
If more than one function is graphed, use to select the desired curve. Enter the x-coordinate of the point on the curve for which the value of the derivative is needed (or trace the curve to the approximate point) and press . The value (or approximate value) of dy/dx at the point is displayed at the bottom of the screen.
Note: The degree of accuracy of the displayed value for dy/dx will usually depend on which derivative setting is selected in MODE. dxDer1 will typically be more accurate than dxNDer. However, dxNDer is less restrictive and the accuracy may be increased by choosing a smaller value for d in the tolerance settings, accessed by pressing .