So its not f(-a)= -6?
No, it is -6.
Please excuse me; I think that I must have skipped over the second line of your original post.
I mean, I did not realize that you had already asked this question.
f(-a) = -6 because f is an odd function.
i thought i have to find f(-a) not tan(a).
That is correct, but you need to realize that f(-a) = tan(-a)
the given tan data is just to tell you that tan data is odd.
No, I don't think so.
tan(data) is given to DEFINE function f.
In other words, function f and the tangent function are one in the same. They just changed the function's name from "tan" to "f", and data = a.