What is a pulsar?

a. the remains of a low-mass star after it explodes
b. a spinning neutron star emitted radio waves
c. another name for a protostar
d. the stage before a dying star becomes a supernova

Suppose that f : rn → rm and that a ∈ k, where k is a connected subset of rn . suppose further that for each x ∈ k there exists a δx > 0 such that f(x) = f(y) for all y ∈ bδx (x). prove that f is constant on k; that is, f(x) = f(a) for all x ∈ k