Let A ? ? and define f: A ? ? by f(x) = ceil(x). Define the set A to ensure that f is injective on A. Solution since range of ceil function is all the integers. so for f to be injective, f should be one-one. and f to be one-one there should not exist two elements in domain that is in A such that when we apply f on that elements output is same. and it will be possible only when A = (set of all integers).