Which function has a range of (-pi/2,pi/2)? y = Cos-1x
y = Tan-1x
y = Sec-1x
y = Csc-1x

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.