Finding Reciprocal Functions SEC, CSC, COT on TI-30XA

First, you may want to refresh your memory of the regular trig functions:

Now, let’s find \csc \frac{5\pi }{4}.
If we look it up on WolframAlpha, we find that it equals -\sqrt{2}, or, roughly, -1.4142.

To get this answer on the TI-30XA, first remember that \csc is equal to \frac{1}{\sin }.

So, what we’re looking for could be expressed as \frac{1}{\sin \frac{5\pi }{4}}. Once we know this, we can type 5\cdot \pi into the TI-30XA.

This gives us ~15.7. (Make sure you’re in radian mode. If not, press the DRG button — located by the 2nd button, upper-left — until you see RAD appear in small letters on the screen.)

Now, we can divide 15.7 by 4. This gives us 3.925. If we take the \sin of this (by pressing the “sin” button while 3.925 is displayed), we get -0.7. IF we divide 1 by -0.7, we get -1.43. As you can see, this is close to the correct value. You can get a more exact value by using the STO function on the calculator. [Press “STO” while a number is displayed on screen and then the number “1” on the keypad. Press the clear button (ON/C). Now, press RCL and the number “1” on the keypad. Your saved value should appear.]

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