Casio fx-CG50 field manual for IB Math
Reading a graph: trace and zoom
Move a cursor along a plotted curve to read coordinates from it, and use the zoom menu to choose the viewing window deliberately.
Trace the graph of y=x−32x+1 to read coordinates from it, and use the zoom menu to locate its vertical asymptote.
Trace walks the cursor along the curve. With a graph on screen press (Trace). A cursor appears on the curve and the coordinates are printed at the bottom of the screen. and move it along, and and switch between curves when more than one is drawn.
Trace moves one pixel at a time. The Casio's graph area is wider than the other two calculators', which means its trace is a little finer for the same window, but the principle is identical: the precision of a trace is the width of the window divided by the number of pixels across. To read more figures you shrink the window, not press the arrow more carefully.
Typing a number jumps straight there. While tracing, type a value and press : the cursor goes to that x directly.
The zoom menu. (Zoom) offers BOX, which snaps the window to a rectangle you draw with two corner presses; IN and OUT, which scale about the cursor; and AUTO, which keeps the x-range and rescales y to fit the curve. BOX is usually the most useful: it snaps the window to the rectangle you drew.
Or set the window by hand. (V-Window) takes Xmin, Xmax, Ymin and Ymax directly, and its INIT option resets to the standard view when the window has become unusable. When a question names the domain, type it rather than zooming towards it.
Tip: use trace to pin down a vertical asymptote. No calculator has an asymptote finder, but trace will bracket one. Graph y=x−32x+1 and trace rightwards towards x=3. The y-readout runs steeply negative and then flips to a large positive value in a single step: the asymptote lies between the last two x-values you saw.
Narrow the window by hand, not with a box. Near the asymptote the curve plunges far outside any small y-range, so a zoom box drawn there would contain no curve at all. Open (V-Window), type the bracket into x, and open y wide, for example −1000 to 1000, so both branches stay on screen. Trace again, and the jump between the two branches narrows the bracket by the same factor as the window.
The vertical asymptote is at x=3.00 to 3 s.f. To read any value from a graph more precisely, shrink the window and trace again.