Answer:
Pi/4
Explanation:
first we have to figure out what cos of 7pi/4 is. Using the unit circle, we know that it is equal to root2/2. Cos to the negative 1 is basically just finding the radian value that matches the value in the parenthesis. This means we have to find the corresponding radian to root2/2. Using the unit circle, we find this to be pi/4