Plane Curvilinear Motion - n-t Coordinates

The n-t coordinate velocity and acceleration equations are given below. What changes when considering circular motion?

v = ρ(dθ/dt) e_t        a = (dv/dt)e_t + (v²/ρ)e_n

The speed remains constant.
The acceleration remains constant.
The radius remains constant.

We can rearrange the n-t equations for circular motion.

v= r(dθ/dt)

a = (dv/dt)e_t + (v²/r)e_n = r(d ²θ/dt ²)e_t + r(dθ/dt) ²e_n