Operations:   Finding MAX or MIN coordinates


While finding a max or min point by "hand" can require calculus, the TI-83 can do it in a moment.

  1. Press Y= and enter the desired function.  For example:  y = x3 - 5x
  2. Press GRAPH:   wpe1.jpg (3768 bytes)wpe2.jpg (6580 bytes)
  3. To find the minimum point in quadrant IV, Press 2nd-TRACE (CALC)
  4. Press the "3" since this is a minimum point.
  5. Now the routine begins:                        wpe3.jpg (4568 bytes)
    bulletThe calculator needs an interval to "look" in.  So first, choose a spot along the graph that is to the LEFT of the minimum point.  Do this by either entering a number, OR moving the arrow keys.
    Then hit ENTER    wpe4.jpg (4944 bytes)
    bulletFollow the same procedure for the RIGHT bound. 
    The smaller the interval, the better.
    bullet"Guess" means, essentially, that the calculator wants a place in the interval to begin looking.   Either enter a number OR move the cursor as close to the minimum point as possible, then press ENTER.

    wpe6.jpg (4707 bytes)
    The coordinates displayed at the bottom of the screen are those of the minimum point.   Round as needed.





    Finding MAXIMUM points is done in the same way.

    REMINDER:  Always choose a SMALL interval when prompted for LEFT and RIGHT bounds.  Stay as close to the max or min point as you can.