Question

Q. Which of the following curves are regular?
(i) γ(t) = (cos^2 t, sin^2 t) for -∞<t<∞
(ii) γ(t) = (cos^2 t, sin^2 t) for 0<t<π/2
(iii) γ(t) = (t, cosh t) for -∞<t<∞
Find unit speed reparametrisation of regular curve(s).