We assume that the function is as follows:

Then, we have that:

Thus, if we have that:

Therefore, the value for the function is f^-1(2) = -1/2 or
Answer:
∠2 = 150°, it is a supplementary angle to 30°
∠3 = 30°, it is an alternate angle to 30°
∠4 = 150°, it is a supplementary angle to 30°
∠5 = 30°, it is an alternate angle to 30°
∠6 = 150°, it is a supplementary angle to 30°
∠7 = 30°, it is an alternate angle to 30°
∠8 = 150°, it is a supplementary angle to 30°