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How to draw a tangent line on a graph on a TI-84 Plus CE, TI-84 Plus or TI-83 Plus

By E-Code · updated

Graph the function, press 2nd DRAW (above PRGM) and 5 for Tangent(, type the X value (or move there with ◀ ▶) and press ENTER. The tangent line is drawn and its equation shown: for X² at X = 1 it is y=2X+-1, that is y = 2X − 1.

Before you start

Type the function into the Y= editor first: this guide uses Y1 = X² (Y=, X,T,θ,n, x², then 2nd QUIT).

Y= X,T,θ,n X² 2nd MODE

Step by step

  1. Draw the graph. GRAPH Press GRAPH. Y1 = X² is already typed in for you.
  2. Open DRAW. 2nd PRGM Press 2nd, then PRGM. DRAW (written above PRGM) holds the drawing tools.
  3. Pick Tangent(. 5 Press 5 for Tangent(. A cursor sits on the curve; ◀ ▶ would move it.
  4. Pick the point. 1 Type 1: the tangent at X = 1.
  5. Draw it. ENTER Press ENTER. The tangent line is drawn, and its equation appears at the bottom.
  6. Read the equation. y = 2X + -1, that is y = 2X − 1: the line that just touches X² at X = 1, with slope 2. 2nd DRAW 1 (ClrDraw) wipes it.

What the screen shows

y = 2X + -1, that is y = 2X − 1: the line that just touches X² at X = 1, with slope 2. 2nd DRAW 1 (ClrDraw) wipes it.

Look for y=2X+-1 on the screen.

Try it with the keys lit up

This guide is one of E-Code's Learn lessons. Open it on E-Code's TI-84 calculator and each key lights up in turn as you press it.

Try “Draw a tangent line on a graph” on the TI-84 calculator

Related

Math programs for the TI-84 Plus CE:

All TI-84 calculus guides · All TI-84 guides · All calculator guides