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 (Y3T=Y1T+Y2T) is always 800.
8. Press † to move the cursor onto the function for interest defined by
X2T and Y2T. Enter 240.