I am using a TI 84 to work on a Matrix problem. After I have pressed 2nd Quit and saved Matrix A, what key strokes do I do to find the inverse

Make sure the calculator is set to degrees. Press MODE and ensure that "DEGREE" is highlighted on the third line. Press 2ND QUIT to get out of the mode screen.

To calculate the inverse sine of 42/57, press
2ND SIN^-1 4 2 / 5 7 ENTER

The arcsine of 42/57 is about 47.46 degrees.

That depends on what you want to invert.

If you want the multiplicative inverse (1/x) then it's the "1-superscript-minus-one" key just below the "MATH" key.

If you want the additive inverse then it's the "(-)" key just to the right of the decimal point key.

If you want the inverse of many of the built-in functions (like the trig functions) then press the "2ND" key at the upper-left before pressing the function key.

For the inverse of some functions you'll have to go through the menus.

If you have a particular inverse in mind, please reply to this post and specify exactly what you'd like to invert.

To get the inverse trigonometric functions press the 2nd key then the trig function key. If you'll look at the key legends above the SIN, COS, and TAN keys you'll see the standard math notations for their inverse function.

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.

It is much more enlightning to tell us what you want to do rather than talk about something that does not exist. And one thing that does not mean anything is that ellusive INVERSE key that everyone and his dog is looking for.
The additive inverse of a number a is its opposite (-a). The key to use is the change key (-).
The multiplicative inverse of non-zero number a is its reciprocal 1/a
The inverse of the natural log (LN) function is the EXPONENTIAL function e^(x). On most calculators if one function is accessed diectly (the marking is on the key), its inverse is accessed by pressing [SHIF] (Casio, or [2nd] (TI) or [2ndF] (Sharp).
The inverse of the function raise 10 to a power [10^x] is [LOG]
Similarly, the inverse of the sine function SIN is the arcsine [sin^-1]. To access the latter, it you press [2nd][SIN]. The same is true for arcosine [2nd][COS], and arctangent [2nd][TAN]

The inverse of the square functions [x^2] is the square root function [2nd][x^2]
Inverse of x^3 is cubic root
This is just a quick overview.

Hi Robert9004x2,

If you want to examine the matrix you want to inverse and, the one that is given you trouble pressing [2nd] [MATRX]. Then stroll and, select the one you want to look at by pressing, [ENTER]. You'll have to press, [ENTER] again and, matrix should display at the Home screen. At the Home when you get to them your looking for the ones that are not square, like 2 by2 or 4 by 4 etc. You might need to re-edit this matrix so, that it is square.

Your trying to invert a matrix that isn't square you might be using using the proper key sequence to create a inverse matrix. Here what the correct inverse matrix look on the Ti 84 Plus Home screen.

And pictured below is a Matrix is being inverted by using the ^ and the -1 keys. Which to inverse a Matrix on the Ti 84 Plus you have to use the [x^-1] key.

This is not the proper way to inverse a Matrix on the Ti 84 Plus. The proper way to inverse of a matrix, the [x-1] key must be used, instead of pressing the sequence [^][-][1]. The [x-1] key is the official inverse key and is located right under the Math key. It is also the same key that you use to get to the matrix menus. The [^][-][1] sequence is only raising the matrix to the -1 power and, will cause an error too. If you need any more help, just post a comment and, I'll respond quickly.

The x^-1 key is in the leftmost column of the keyboard, below the MATH key.

If you want the inverse trig functions, press 2ND then the trig function key.

A singular matrix has no inverse. It's the equivalent of zero: trying to take the inverse of zero is an error. Check the matrix to make sure you have entered it correctly. If the error persists, could you post the matrix in question?

1. Press [2nd] [X to -1] under [MATH[ to access the (Matrix) menus.
2. Use right arrow to highlight [EDIT]
3. Press [1:A] to edit (create from scratch) the A matrix.
4. On the line MATRIX[A] line cursor blinks on 1
5. Enter m dimension (3) and press [ENTER].
6. Cursor moves to the second dimension (n). type 3.
7. Press [ENTER].
8. A 3x3 matrix template is displayed with A_11 element highlighted.
9. Replace the value 0 with your value for A_11.
10. Press [ENTER].
11. Type a value and press [ENTER].
12. When finished, press [2nd][QUIT] to exit the matrix editor.
    

Your matrix is ready to be operated on (squaring, multiplication by a scalar, inverse if matrix is non-singular, determinant.) All operations are available under [2nd][X^-1](Matrix) [=>][MATH].

Hello,
The inverse tangent or arctangent shares the ame key as tan. You access it by pressing [2nd][tan] number [)] [ENTER]. Be warned! The angle value displayed is the same as the one set in [MODE].
Hope it helps