TI-30xa Calculator Reciprocal Key

Use the key x-1.
Example: reciprocal of 5: Press 5, then key x-1, then =

Your question is not clear. To calculate the reciprocal of a number on display use the x^-1 or 1/x key, or just enter 1/ number.

Enter the number and press the = sign.
With the number displayed, press the power key (marked as [X^y], [Y^x] or [^]) followed by exponent -1.
OR while the number is stored in Ans memory, enter 1 / Ans.
Some calculators have a special key for the reciprocal. It is marked as [x^-1]. By pressing the reciprocal key while number is displayed, you calculate its reciprocal.

Use the 1/x key or the general power key x^-1.
By hand 0.6=3/5
The reciprocal of 3/5 is 5/3

It's the second function of the "2" key, marked "x-superscript-negative-one".

[H+]=10^(-8.19). The - sign is the change sign key. The result is 1.2589x10^(-9)

There is a key on the left column of keys, below the MATH key and above the x^2 key. It is marked with an x raised to power of -1.
It computes the reciprocal of the number displayed.

There isn't a cosecant key. Use the relationship
 csc(x) = 1 / sin(x)

Compute the sine and take its reciprocal.

The cosecant function does not have a specific key on any calculator because it can be easily calculated as the reciprocal of sine.
Thus csc(-330°)=1/sin(-330°)=2
sin(-330°)=sin(360°-330°)=sin(30°)=0.5
csc(-330°)=1/0.5=2
If you do not want to be bothered with these facts, just calculate the sine of -330° and take the reciprocal of the result using the [x^-1] key. For the minus sign before 330, use the change sign key (-). Close the right parenthesis.

[SIN] [(-)] 330 [)] [x^-1]

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