HP 39g Graphing Calculator - Manual (Page 92)

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:
-V = Vnf +
at
2
where ,v is distance, vq is initial velocity, t is time, and a is
acceleration. This is actually tn’o equations, y = x and
y = V q t + ( a P ) / 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 di.stance
makes sense.
1. Select the Solve aplet and enter the equation.
I
APLET
I
Select Solve
HEU
I
alpha IXB
2
.
fALPHAlV [xllALPHAlT
[+11 alpha ] A
[ x ]( alpha ]T[ x 5]02
: dlve svmmlic viehs
■PEliX=V*T+fl*TgA2
E3:
E4:
E5:
jgtniBimi ■ WilililljtW
Find the solution for T (time) when A=30, V=2, and
A=4. Enter the values for X, V, and A; then highlight the
independent variable, T.
NUM
30 I ENTER I
2 I ENTER I
[T|4 I ENTER I
py] fvl to highlight T
sSOLVE NUMEiilC VIEWS
ENTER VmUE Oli PRESS SOLVE_______
Solve aplet