How to Graph Trig Functions on the TI-84 Evo

Graphing a trig function on the TI-84 Evo is like graphing anything else, but the viewing window and the angle mode are what decide whether the wave actually looks right.

Graph a sine wave

  1. Press Y=. It's the top-left key, and it opens the function editor with the cursor on Y1.
  2. Type the function. Press sin, then the X key just right of alpha, so the line reads Y1=sin(X. You don't need to close the parenthesis.
    The TI-84 Evo Y= editor showing Y1 equals sin of X
  3. Press graph. The wave draws, but on the standard window it's squeezed into a thin band across the middle.
    A sine wave squeezed into a thin band on the TI-84 Evo standard graphing window

The fast way: ZTrig

Press zoom and choose 7:ZTrig. In one press it sizes the window to a wave and matches your angle mode, so the sine curve fills the screen. The tick marks along the x-axis are now π/2 apart, a quarter turn each.

The TI-84 Evo sine wave filling the screen after ZTrig

Set the window yourself

ZTrig always gives the same fixed frame. To choose your own view, press window and set the edges by hand.

For X, a couple of full waves reads well. Set Xmin to -2π and Xmax to 2π. You can type π right in the window as 2nd then ÷, and the calculator turns it into a decimal.

Leave the scale at π/2 so a tick mark lands on each quarter turn, and set Y from -2 to 2, enough room for a wave that only reaches 1.

The TI-84 Evo WINDOW screen set to Xmin -2 pi, Xmax 2 pi, Xscl pi over 2, Ymin -2, Ymax 2

Press graph for exactly two clean periods, framed the way you chose.

The TI-84 Evo showing two clean sine periods on a custom window

Choosing Y yourself matters most for taller waves. Graph something like 5sin(X), and ZTrig's fixed height cuts the peaks off:

The graph of 5 sin X with its peaks cut off the top and bottom by ZTrig on the TI-84 Evo

Give Ymin and Ymax room past the top of the wave, like -6 and 6, and it fits.

The graph of 5 sin X fully in view after setting Ymin to -6 and Ymax to 6 on the TI-84 Evo

Radians or degrees

The calculator draws in whatever angle mode it's set to, and it starts in radians. If your wave looks flat or scrambled, the mode and the window don't match:

A sine graph flattened to a near-straight line because the TI-84 Evo is in degree mode on a radian-sized window

Switch the mode in the mode menu (here's how to switch between degree and radian mode), then press ZTrig again and the graph reframes to fit the mode you're in.

Good to know

  • Tangent looks different. Graph tan(X) the same way. It draws as steep branches with vertical gaps between them, not a smooth wave.
    The TI-84 Evo graphing tangent as a series of steep branches with vertical gaps
  • Cosine works just like sine. Enter cos(X) on any Y line and it graphs the same way.
  • No secant, cosecant, or cotangent key. The keyboard only has sin, cos, and tan, so build the other three as fractions: secant is 1÷cos(X), cosecant is 1÷sin(X), and cotangent is 1÷tan(X). Here's secant entered that way.
    The TI-84 Evo graphing secant as 1 divided by cos of X, showing repeating U-shaped curves
  • The rest of the graphing keys work here too. Trace, zoom, and the window fields behave the same as with any graph. See how to graph a function for those.