Find Derivatives of Polar Equations with the TI-83 Plus
You can use the TI-83 Plus graphing calculator to find derivatives of polar equations. To find the derivative of a polar equation at a specified value of
follow these steps:
Graph the polar equation in a viewing window that contains the specified value of
To get a viewing window containing the specified value of
that value must be between
Set the Format menu to ExprOn and CoordOn.
Press [2nd][TRACE] to access the Calculate menu.
Press  or  to respectively select the dy/dx or
If necessary, repeatedly press
until the appropriate polar equation appears at the top of the screen.
Enter the specified value of
To do so, use the keypad to enter the value of
As you use the keypad,
= replaces the coordinates of the cursor location appearing at the bottom of the screen in the previous step. The number you key in is placed after
=. If you make a mistake when entering your number, press [CLEAR] and re-enter the number.
If you’re interested only in finding the slope of the curve in a general area of the graph — instead of at a specific value of
then just use the
to move the cursor to the desired location on the graph (instead of entering a value of
After pressing [ENTER], the derivative is displayed at the bottom of the screen.