Texas Instruments TI-83 PLUS - Manual (Page 597)

TI-83 Plus Activities 594
6. Press p . Set these window variables.
Tmin=1 Xmin=0 Ymin=0
Tmax=360 Xmax=360 Ymax=1000
Tstep=12 Xscl=10 Yscl=100
Tip: To increase the graph speed, change Tstep to 24 .
7. Press r . After the graph is drawn, press 240
Í to move the
trace cursor to T=240 , which is equivalent to 20 years of payments.
The graph shows that for the 240th payment ( X=240 ), 358.03 of the
800 payment is applied to principal ( Y=358.03 ).
Note: The sum of the payments ( Y 3T =Y 1T +Y 2T ) is always 800.
8. Press † to move the cursor onto the function for interest defined by
X 2T
and Y 2T
. Enter 240 .