Trident Help

Natural Scientific 991 manual · Chapter 7 of 18

Variables and memory

Store values in A to F, x, y and M, recall them, add to memory with M+, and re-run formulas with CALC.

7.1Store a value in a variable#

There are nine variables: A, B, C, D, E, F, x, y and M. To store a value, calculate it (or leave it as the last answer), press SHIFTSTORCL (STO) and then the variable key with its red letter. The STO indicator shows while the calculator waits for the letter.

Example 7.1

Store 5 in A and use it

  1. Type 5, then STO and the A key (the minus-sign key).

    5SHIFTSTORCL(−)

  2. Type A + 1: ALPHA, the A key, plus 1.

    ALPHAA(−)+1=
Result of the example "Store 5 in A and use it" The display shows: A+1 / 6.
You should seeA+1 6
Example 7.2

Store in x

  1. Store 4 in x (the right-bracket key).

    4SHIFTSTORCL)

  2. x squared.

    ALPHAx)x²=
Result of the example "Store in x" The display shows: x² / 16.
You should see16
  1. Value on screen
  2. SHIFTSTORCL
  3. (−) (A)
  4. Value is in A
Store a value in A

7.2See what is stored#

Press RCL to list the value of every variable, two per line. Use ▼ to scroll down to M, and AC to close the list.

Example 7.3

The RCL list

  1. Store 7 in x, then press RCL.

    7SHIFTSTORCL)RCL
Result of the example "The RCL list" The display shows: A=0 B=0 / C=0 D=0 / E=0 F=0 / x=7 y=0.
You should seex=7
The RCL list of variables The display shows: A=0 B=0 / C=0 D=0 / E=0 F=0 / x=7 y=0.
The RCL list of variables

7.3Add to and subtract from memory M#

M+ adds the current answer to M and SHIFTM−M+ subtracts it. The M indicator lights when M is not zero. Type ALPHAMM+ to use M in a calculation.

Example 7.4

Accumulate in M

  1. Calculate 3 and add it to M. Then 4.

    3=M+4=M+

  2. Recall M.

    ALPHAMM+=
Result of the example "Accumulate in M" The display shows: M / 7.
You should see7
Example 7.5

Subtract from M

  1. Add 3 to M, then subtract 1.

    3=M+1=SHIFTM−M+

  2. Recall M.

    ALPHAMM+=
Result of the example "Subtract from M" The display shows: M / 2.
You should see2

7.4Re-run a formula with new values (CALC)#

Type an expression that uses variables, then press CALC. The calculator asks for each variable in turn: type a value and press =. It then shows the result. Press CALC again to run the same formula with other values.

Example 7.6

Evaluate x² + 1 at x = 3

  1. Type x² + 1.

    ALPHAx)x²+1

  2. Press CALC, enter 3.

    CALC3=
Result of the example "Evaluate x² + 1 at x = 3" The display shows: x²+1 / 10.
You should see10
Example 7.7

Several variables

  1. Type A × x + B.

    ALPHAA(−)×ALPHAx)+ALPHAB°'"

  2. CALC, then A = 2, x = 3, B = 4.

    CALC2=3=4=
Result of the example "Several variables" The display shows: A×x+B / 10.
You should see10
Example 7.8

Run it again

  1. Type x² + 1, run with 3.

    ALPHAx)x²+1CALC3=

  2. CALC again, with 4.

    CALC4=
Result of the example "Run it again" The display shows: x²+1 / 17.
You should see17

7.5Solve an equation for x (SOLVE)#

Type an equation using x. Press ALPHA=CALC for the equals sign. An expression without an equals sign is solved for 0. Press SHIFTSOLVECALC (SOLVE), type a starting guess near the answer and press =. The result shows x and L−R, how close the two sides are (0 means exact). The solution is also stored in x.

Example 7.9

Solve x² − 4 = 0

x2−4=0x^2-4=0

  1. Type x² − 4 = 0.

    ALPHAx)x²−4ALPHA=CALC0

  2. SOLVE, guess 3.

    SHIFTSOLVECALC3=
Result of the example "Solve x² − 4 = 0" The display shows: x²−4=0 / x=2 / L−R=0.
You should seex=2 L−R=0
Example 7.10

A different guess finds the other root

  1. Same equation, guess -3.

    ALPHAx)x²−4ALPHA=CALC0SHIFTSOLVECALC(−)3=
Result of the example "A different guess finds the other root" The display shows: x²−4=0 / x=-2 / L−R=0.
You should seex=-2
Example 7.11

Solve without an equals sign

  1. Type 2x − 6.

    2ALPHAx)−6

  2. SOLVE, guess 0.

    SHIFTSOLVECALC0=
Result of the example "Solve without an equals sign" The display shows: 2x−6 / x=3 / L−R=0.
You should seex=3
  1. Type the equation
  2. ALPHA=CALC for =
  3. SHIFTSOLVECALC
  4. Guess
  5. =
Solving an equation

7.6Clear the variables#

Press SHIFTRESET9 then 2 (Variable Memory) to set every variable and Ans back to 0. Choosing 3 (Initialize All) also clears history and all settings.

Example 7.12

Clear variable A

  1. Store 5 in A, reset variables, then look at A.

    5SHIFTSTORCL(−)SHIFTRESET92ALPHAA(−)=
Result of the example "Clear variable A" The display shows: A / 0.
You should see0

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