Question

Is the trig function: even, odd, neither `y=cosx`?

Answer 1

It is even since `cos(-x)=cosx AA x in RR`

Explanation:

By definition, `f` is an odd function if `f(-x)=-f(x)`
`f` is an even function if `f(-x)=f(x)`

Since `cos(-x) = cosx` for all `x in RR`, it implies that `f(x)=cosx` is an even function.