Operation Topics:
Clear and Delete
Order of Operations

Change the mode screen to the settings below. Remember that running a program may change the mode setting.

Clear and Delete

Type the number 12345 and do NOT press ENTER. The cursor should be placed to the right if the number 5.

If you want to clear the last character, press the delete key.

Press the delete key to delete the 5.

If you would like to delete the character 1 in the expression above, press the left section of the cursor pad to move the cursor to the right side of the 1. Then press the delete key. To highlight and expression, hold down the shift key and scroll to the left or right.

To quickly move the cursor to either the right or left side of an expression, press the 2nd key then the right or left arrow on the cursor pad.

The CLEAR button will clear the whole or the highlighted part of an expression on the entry line. Press the CLEAR button (located to the left of the cursor pad) to clear the entry line.

Again, type the expression 12345 and this time press the ENTER button. This will move the entry to the history area.

Note that the expression 12345 also remains on the entry line.

To clear the history area, press F1 then 8: (Clear Home).

You may also clear expressions from the history area by scrolling through and pressing the delete key. Above the delete key , are standard insert (INS) and delete (DEL) options.

Exercises
Order of Operations

When evaluating an expression, be sure to remember the Equation Operating System (EOS) hierarchy. All of the order of operations are listed in Appendix B of the TI-91 GUIDEBOOK. Some of the more common operations are

1.) Parentheses ( ), brackets [], braces {}

2.) Function calls

3.) Post operators: degrees, minutes, seconds, factorial, percentage and radians.

4.) Exponentiation, power operator (^)

5.) Negation (-)

6.) Multiplication (*), division (/)

7.) Addition (+), subtraction (-)

8.) Equality relations

The EOS indicates which calculator instruction will execute first, then second, etc. The TI-92 executes parentheses first, then function calls ,post operators and so on. If you have any doubt about a hierarchy be sure to use parentheses () to supersede an instruction.

Order of Operations

To enter the number -5, first select the negation key (not the subtraction key ) then the 5.

Multiply the -5 times 2 by typing -5*2 then ENTER. Note that the answer -10 is on the right side of the history area and the 0/30 in the status line changes to 1/30.

Evaluate -22 and (-2)-2 . To raise an expression to a power, use the carrot (^) key (located under the cursor pad). Why are the answers different?

Next ,enter the number 2.3 x 10-12 in scientific notation. Enter 2.3 then press then EE and -12.

Multiply this number by 5.6 x 10-11 . You may see the term ans(1) in the entry line. This represents the previously entered expression. An ans(2) represents the answer above ans(1). Keep multiplying the results by .01 until the answer on the right side of the screen changes to scientific notation.

Now take the time to view the MODE screen Display Digits.

Note that the display digit option is FLOAT 6.

To evaluate the term , enter the square root function by pressing 2nd and the multiplication sign. Then enclose the 3 by parenthesis and divide by 2.

Note that the solution is exact and in pretty print. In some applications an approximate or floating point solution is preferable. The are two techniques to obtaining an approximate solution. The mode can be changed, or you can press the diamond key then the ENTER key.

Other

See if you can evaluate the following expressions. You may have to change the mode of the calculator to get the desired result.

Evaluate 5!. The answer is 120.

Evaluate the exact and approximate solution to sinin radians. The answers are below.