Some Quick Hints for TI 89 use in College Algebra and Trigonometry
This guide is meant to provide a few pointers on using some of the more tricky but common features of the TI 89 calculator in the College Algebra and Trigonometry courses. For a more detailed guide refer to the owners manual.
Graphing Related Operations
Finding Intersection of two Curves: To find the intersection of two curves, click F5(Math) then 5(Intersection). Then click once on each curve. Then click to the left of the intersection for the lower bound and to the right for the upper bound.
Defining Piecewise Functions: To define a piecewise function, use the when command which you will need to type in using the alpha keys. for example
when(x<0,x-3,cos(x))
graphs
Polar and Parametric Equations: To graph polar or parametric equations, click Mode then change the graph to Polar or to Parametric.
Finding Roots: To find a root on a graph, click F5(Math) then 2(Zero) then move the cursor to the left of the root. Hit enter, then move to the right of the root and hit enter.
Shading Inequalities: To shade above or below a graph, click F5(Math) then C(Shade) and follow the instructions.
Operations
!: You can find the ! key by clicking MATH then 7(Probability) then !
Approximate Answers: To get a decimal
approximation of a number hit the green diamond key 
Combinations: Click MATH then 7(Probability) then 2(nCr). For example nCr(5,2).
Complex Numbers: To enter a complex number, use the i key. For example (2 + 3i)*(1 - i) will multiply the complex numbers.
Degrees/Minutes/Seconds: Use '
and " to indicate minutes and
seconds. To change to degrees, minutes and seconds click MATH
then angle then DMS. For example 45.371
DMS.
Infinity: Note that the TI89 can handle 
.
Matrices: To input a matrix use APPs then Data/Matrix Editor then New. Then change Data to Matrix. Put in the name such as "AA" in the variable field. Then enter row and column dimensions. Then edit as a spread sheet. Use F6(util) to delete a column or row. To manipulate matrices, exit the matrix application, then go to MATH then Matrix. Notice that J(RowOpps) is available.
Permutations: Click MATH then 7(Probability) then 2(nPr). For example nPr(5,2).
Polar and Rectangular Coordinates: To
change from polar coordinates to rectangular coordinates or from rectangular
coordinates to polar coordinates, click MATH then angle
then P Rx
and P Ry
(polar to rectangular).
Sequences: To explore sequences, click Mode then change the graph property to SEQUENCE. Then in Y= put in the sequence. For example, y = n2 - n. Then click on graph or table to see the sequence.
Series: To evaluate a series ckick on MATH
then A(Calculus) then S(Sum).
The syntax is S(f(x),x,a,b).
Note that infinite series are allowed. Try S(1/x2,x,1,)
Split Screen: To view more than one screen
hit MODE then Split Screen,
then choose TOP-BOTTOM or LEFT-RIGHT.
To make the other side active, use the 
button.
Unit Conversions: To convert 5 fathoms to cm, click 5 then UNITS then in length
click _fath. Then click the orange
key. Then
click UNITS again and in length click _cm.
Vectors: To input a vector, use the square brackets. For example [2,3] means 2i + 3j. Add and subtract as you would expect.