Question

What trigonometric ratios of angles from $0^o$ to ${90}^o$ are not defined?

Answer 1

The trigonometric table of all the functions with all values are shown in the above table:

Hence, from the above table we observe that between $0^o$ to ${90}^o$, the below trigonometric functions are equal to not defined.

$\tan \frac{\pi }{2}=\csc 0^o=\cot 0^o=\sec \frac{\pi }{2}=$ Not defined