You typed a function, pressed graph, and saw either a flat line or a spiky diagonal. The problem is almost always the window, not the function. Press zoom and work through this.
The six presets you'll actually use
1:ZBox — rubber-band zoom. Arrow to one corner of the region you want, press enter, arrow to the opposite corner, press enter again. The calculator zooms into that box. Best for inspecting a specific intersection or root.
2:Zoom In / 3:Zoom Out — zoom around the cursor by a factor of 4 each time. Set the cursor first: press graph, use arrow keys to position.
4:ZDecimal — sets x from −4.7 to 4.7 with ΔX = 0.1. Useful for polynomial roots that happen to land on tenths. Also the only preset where moving the cursor shows clean 0.1 steps.
5:ZSquare — adjusts the current window so x-units and y-units are the same pixel width. Circles look like circles. Perpendicular lines look perpendicular. Critical for geometry problems.
6:ZStandard — resets to the default [-10, 10] × [-10, 10]. Use this when you're lost — get back to a known state.
0:ZoomFit — the most under-used preset. Keeps the current X-range, but auto-adjusts Ymin/Ymax to show the full range of y-values over that X-range. If you're plotting y = sin(5x) in a default window and only seeing a line, ZoomFit rescales Y to [-1, 1] and the curve appears.
The manual window key
Press window. You'll see Xmin, Xmax, Xscl (tick spacing), Ymin, Ymax, Yscl, Xres.
When you know the domain you care about, type it directly:
Xmin = 0
Xmax = 2π (enter as 2 * 2nd + ^ which is π, or just 6.28)
Ymin = -1.5
Ymax = 1.5
That gives a clean single-period sine wave with headroom above and below.
A common student trick: ZoomStat
Not on the zoom menu by default. Access: zoom → 9:ZoomStat. It auto-sets the window to fit a STAT PLOT — perfect after entering data in L1/L2. Saves tweaking when you don't know the data range.
The Xres setting
Xres controls how many pixels between each evaluated x-value. Xres = 1 is highest detail (every pixel). Xres = 8 is fastest (every 8th pixel). Crank it to 1 for smooth curves; crank it to 4 or 8 for messy functions that take a long time to render.
Restoring a good window after you broke it
Typed Xmax = Xmin by accident and now graph shows an error? Press zoom → 6:ZStandard. Known good defaults. Start over from there.
Gotcha
Xscl and Yscl only affect the tick marks, not the axis range. If your graph looks right but the labeled gridlines are missing, check Xscl. Xscl = 0 disables tick marks entirely.