Enter your function as Y1.
Press [GRAPH] to graph the function.
To select the Draw Tangent Line function use the DRAW menu.
To view the DRAW menu, press [2ndF] [STAT].
Choose option A DRAW, 5 T_Line(.
Move the cursor along the graph using the left (.) or right (.)
arrow keys to the desired location for the tangent line.
Press [ENTER] to draw the tangent line at that location.