How do i get inv on my TI-84 Plus caculator

Possible: Inverse trigonometric functions have limited domains. For arcsine and arccosine it is between -1 and 1.

Is it somehow preventing you from graphing, or are you simply not getting the graph you expect?

Most likely you have the angular mode set wrong. You probably want it set to radians. Press MODE, move to the third line, highlight RADIAN, press ENTER, then 2ND [QUIT].

If it's not the angular mode, please reply to this post and give an example or two.

The INV key that you may find on some scientific calculators has, on the TI 83/84/ Plus calculators, an equivalent key marked [2nd].

On the TI83/84 Plus, each trigonometric function has a second marking [SIN^-1], [COS^-1] or [TAN^-1]. To calculate the inverses of trigonometric functions ( arc sine, arc cosine, arc tangent) you press [2nd] followed by the relevant trigonometric function key For example, [2nd] [SIN] displays sin^-1( on the command line.

Unfortunately the hyperbolic functions and their inverses are only accessed through the CATALOG. You press [2nd][0] to open the CATALOG. Then you scroll down the CATALOG list to reach cosh(, cosh^-(, sinh(, sinh^-1(, tanh(, or tanh^-1(.
To speed the search in the catalog, you use the ALPHA keyboard: To reach cosh(, press[PRGM] and you scroll down from there.

Make sure the argument is between negative one and positive one, inclusive. The inverse cosine is defined only for arguments in that domain, anything else will give you a domain error.

When you graph functions y=f(x), even if f(x) is a trigonometric function, the default independent variable is x. You will have to use the variable theta only when drawing polar functions.
To draw the sine and cosine or any other trigonometric function set the angle unit to radians and window zoom to standard. If your angle unit is degree you must modify the x-window range to, say, multiples of 180 degrees. Other than that there is nothing special to do. The functions are well-behaved and should graph nicely. You will alos get a better view if Ymin is about -1.2 and Ymax is about 1.2

You're probably trying to graph a function that does not involve stat plot features. You can correct this by turning off the stat plot features. Press "2ND" "STAT PLOT" and then select 4:PlotsOff.

Turn StatPlotsOff to avoid errors:
Press [2nd][STATPLOT][4:PlotsOff][ENTER].

1. Verify that in [MODE] Func is highlighted.
   
2. If it is not, use arrow to highlight Func and press [ENTER[ to validate.
3. Press [Y=] and type in the functions.
   
4. Press [ENTER] at the end of each function.
5. Before pressing [GRAPH], make sure that all the = signs that define the functions to be graphed are highlighted white on black. If one is not highlighted, use arrow to move cursor on the sign and press [ENTER].
6. Select the graph styles: The small piece of line to the left of a Y that defines a function is the style. Move cursor on it and press [ENTER] . Each [ENTER] (on same line) selects another style.
7. Press [GRAPH] to see the graphs.
8. If one of them is missing, verify that its = is still highlighted, then use the [WINDOW] to set the Window dimensions, or the [ZOOM] to adjust.

If you have problems, post a comment to this thread.

I have answered many questions asked by teachers and professors, and very few, if any, deigned to rate the posts. Why do I set myself up for yet another disappointment: I just like to help.

Anyway, the most common source of errors with computation of trigonometric functions is the angle unit. On Ti 83/84Plus (SE) calculators there are two angle units: the degree and the radian.

To verify which angle unit is set as default on a calculator, press MODE. You will see the following screen. The relevant line is the 3rd. On the screen RADIAN is highlighted, meaning that all angle values you feed to trigonometric functions are interpreted as radian measures.
Similarly, all values returned by inverse trigonometric functions are in radians.

I do not know what grades you teach, but if you are doing any differential calculus, the only appropriate unit is the radian. Only for the radian unit is the derivative of sin(x) equal to -cos(x). For the degree, you must introduce a factor to adjust (as a change of variable).

Set all your calculators to use the angle unit you are using in your teaching, and there will be no unexpected results.

It might have gotten wet. If it has, you will have to get another one.

Try the 2ND key instead of INV.