Casio fx-CG50 field manual for IB Math
Finding maxima and minima
Graph a function, tighten the viewing window around the turning points, then use the calculator's maximum and minimum tools to read each coordinate.
Find the local maximum and local minimum of y=ex/4−8x2.
From the MAIN MENU open Graph (icon 5) and type the function on Y1: for the e^▯ template, type , then to leave the exponent box; after that type . Press to register it.
Frame the graph on the standard window: (V-Window) → (STANDRD), then and (DRAW). Both turning points are on screen, but the y-range is much taller than the actual height of the curve, so the maximum and minimum are harder to read precisely.
Zoom in on the part that matters with a box: press (Zoom) → (BOX). Move the cursor above-left of the curve's turning points and press to anchor the first corner; move below-right of them and press again. The dashed marquee shows the region the window will snap to. Make sure it contains both the peak and the valley.
The window snaps to the box. Press (G-Solv) → (MAX). The calculator jumps to the local maximum and prints the coordinates along the bottom.
Then press (G-Solv) → (MIN) to jump to the local minimum. If a graph ever shows more than one candidate of the same type, use and to move between them.
The local maximum is approximately (1.43,1.17) and the local minimum is approximately (8.61,−0.660).
Your turn
Work each one on your calculator, then check the answer.
- 1
Find the coordinates of the local maximum and local minimum of f(x)=ex/3−6x2.
- 2
Find the coordinates of the local maximum and local minimum of f(x)=12x3−x+ln(x+5).
- 3
Find the coordinates of the local maximum and local minimum of f(x)=10x3−x+ex/5.