Tangent Function
The next trigonometric function to be graphed is the tangent function. The tangent function is a little different than the sine and cosine functions because it is undefined at certain points, and therefore, you need to be careful when graphing the function. When the table is created for the tangent function, there are smaller intervals along the x-axis of 
in order to really see what happens with
f(x) = tan(x).
Look at the following table (Und. means undefined):
| x |
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| 0 |
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| tan(x) | Und. | -1 | 0 | 1 | Und. | -1 | 0 | 1 | Und. | -1 | 0 | 1 | Und. |
Why are some of these values undefined? Take a look at
. You need to go back to the Unit Circle:
You know that
In this case:
Remember, you can’t have a zero in the denominator of a fraction.