By using the definition of the inverse cosine function, we will see that:
[tex]cos^{-1}(0) = pi/2[/tex]
How to complete the expression?
We have the expression:
[tex]cos^{-1}(0) = \frac{pi}{?}[/tex]
Remember that if:
[tex]cos(x) = y\\\\cos^{-1}(y) = x[/tex]
Then, in what do we need to evaluate the cosine function to get an output equal to zero?
[tex]cos( pi/2) = 0[/tex]
Then:
[tex]cos^{-1}(0) = pi/2[/tex]
Then we can replace the question sign with a 2.
If you want to learn more about the cosine function, you can read:
https://brainly.com/question/8120556