Question

is y = cos^-1(x) SAME AS
x = cos(y), where 0 < y < π

Answer 1

or x = 1/cos(y), where y is any number other than π/2 times an odd number

Answer 2

go with the first one, since arccosine is a well defined function

Answer 3

how about this one
y = 1/cos(x), where x is any number other than π/2 times an odd number

Answer 4

wouldnt y=1/cos(x) be the same as y = cos^-1(x)