# Using Variables In Equations - HP 40G User Manual

Graphing calculator.

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8. Use this equation to solve for another variable, such as
velocity. How fast must a body's initial velocity be in
order for it to travel 50 m within 3 seconds? Assume the
same acceleration, 4 m/s
initial guess.
3
50
TPGW@—

## Using variables in equations

You can use any of the real variable names, A to Z and θ. Do
not use variable names defined for other types, such as M1 (a
matrix variable).
Home
All home variables (other than those for aplet settings, like
Xmin and Ytick) are global, which means they are shared
variables
throughout the different aplets of the calculator. A value that
is assigned to a home variable anywhere remains with that
variable wherever its name is used.
Therefore, if you have defined a value for T (as in the above
example) in another aplet or even another Solve equation, that
value shows up in the Numeric view for this Solve equation.
When you then redefine the value for T in this Solve equation,
that value is applied to T in all other contexts (until it is
changed again).
This sharing allows you to work on the same problem in
different places (such as HOME and the Solve aplet) without
having to update the value everywhere whenever it is
recalculated.
H I N T
As the Solve aplet uses any existing variable values, be sure
to check for existing variable values that may affect the solve
process. (You can use
in the Solve aplet's Numeric view if you wish.)
Aplet variables
Functions defined in other aplets can also be referenced in the
Solve aplet. For example, if, in the Function aplet, you define
F1(X)=X
to solve the equation X
7-10
manuals search engine
2
. Leave the last value of V as an
to reset all values to zero
CLEAR
2
+10, you can enter F1(X)=50 in the Solve aplet
2
+10=50.
Solve aplet  