If f(x) is defined in [a, b] where a,b ≥ 0, then find the even extension of f(x).
To get even extension replace x by -x, i.e. f(x), here x ∈ [a, b]
⇒ -x ∈ [ -b,-a] ⇒ domain
[To understand how we get domain, we can consider the function √x. √x is defined for x > 0, whereas the even extension of √x, √−x is not defined when x lt0]