HP 39g+ - Manual (Page 90)

7-8 Solve aplet
Plotting to find guesses
The main reason for plotting in the Solve aplet is to help you
find initial guesses and solutions for those equations that have
difficult-to-find or multiple solutions.
Consider the equation of motion for an accelerating body:
where x is distance, v
0
is initial velocity, t is time, and a is
acceleration. This is actually two equations, y = x and
y = v
0
t + (at 2 ) / 2.
Since this equation is quadratic for t, there can be both a
positive and a negative solution. However, we are concerned
only with positive solutions, since only positive distance
makes sense.
1. Select the Solve aplet and enter the equation.
>$3/(7@ Select
Solve TU6SU—
>$/3+$@X
2•
>$/3+$@V >;@>$/3+$@T
>@>$/3+$@A
>;@>$/3+$@T >;@>j@2
PF—
2. Find the solution for T (time) when X=30, V=2, and
A=4. Enter the values for X, V, and A; then highlight the
independent variable, T.
>180@
30
>(17(5@
2
>(17(5@
*e,4 >(17(5@
*e,*e, to highlight T
x v
0
t
at
2
2
------- + =