How do you evaluate \[{\tan ^{ - 1}}\left( 0 \right)\] without a calculator?

Hint:
Any trigonometric function raised to this negative power means that it is the inverse of that trigonometric function. So, we have to find the inverse of the given trigonometric function. By finding the inverse it means that we have to find the angle which when put into the given trigonometric function, yields the same value as is given in the inverse of the trigonometric function.

Complete step by step solution:
The given trigonometric function is \[{\tan ^{ - 1}}\left( 0 \right)\]. When a trigonometric function is raised to a negative power, it means that we have to find the inverse of the given trigonometric function. By finding the inverse it means that we have to calculate the angle which gives the value which is inside the given inverse of the trigonometric function, which is 0.
So, \[{\tan ^{ - 1}}\left( 0 \right) = 0^\circ \]

Hence, the value of the given trigonometric function is zero \[\left( 0 \right)\].

Note:
So, for solving questions of such type, we first write what has been given to us. Then we write down what we have to find. In the given question, we just needed to know what the negative sign over the given trigonometric function means. Then we just used the concept that we got (which is the inverse of a function) and we simply just found the answer of the question.